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Vulnerability from cleanstart
Published
2026-04-01 09:10
Modified
2026-03-28 10:02
Summary
Security fixes for CVE-2026-25679, CVE-2026-27139, CVE-2026-27142, CVE-2026-33186, ghsa-527x-5wrf-22m2, ghsa-9h8m-3fm2-qjrq, ghsa-c9v3-4pv7-87pr, ghsa-h75p-j8xm-m278, ghsa-p77j-4mvh-x3m3 applied in versions: 1.26.7-r0, 1.26.7-r1, 1.26.7-r2
Details
Multiple security vulnerabilities affect the kubernetes-dns-node-cache-fips package. These issues are resolved in later releases. See references for individual vulnerability details.
References
{
"affected": [
{
"package": {
"ecosystem": "CleanStart",
"name": "kubernetes-dns-node-cache-fips"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "1.26.7-r2"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"credits": [],
"database_specific": {},
"details": "Multiple security vulnerabilities affect the kubernetes-dns-node-cache-fips package. These issues are resolved in later releases. See references for individual vulnerability details.",
"id": "CLEANSTART-2026-MJ07404",
"modified": "2026-03-28T10:02:34Z",
"published": "2026-04-01T09:10:45.280620Z",
"references": [
{
"type": "ADVISORY",
"url": "https://github.com/cleanstart-dev/cleanstart-security-advisories/tree/main/advisories/2026/CLEANSTART-2026-MJ07404.json"
},
{
"type": "WEB",
"url": "https://osv.dev/vulnerability/CVE-2026-25679"
},
{
"type": "WEB",
"url": "https://osv.dev/vulnerability/CVE-2026-27139"
},
{
"type": "WEB",
"url": "https://osv.dev/vulnerability/CVE-2026-27142"
},
{
"type": "WEB",
"url": "https://osv.dev/vulnerability/CVE-2026-33186"
},
{
"type": "WEB",
"url": "https://osv.dev/vulnerability/ghsa-527x-5wrf-22m2"
},
{
"type": "WEB",
"url": "https://osv.dev/vulnerability/ghsa-9h8m-3fm2-qjrq"
},
{
"type": "WEB",
"url": "https://osv.dev/vulnerability/ghsa-c9v3-4pv7-87pr"
},
{
"type": "WEB",
"url": "https://osv.dev/vulnerability/ghsa-h75p-j8xm-m278"
},
{
"type": "WEB",
"url": "https://osv.dev/vulnerability/ghsa-p77j-4mvh-x3m3"
},
{
"type": "WEB",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-25679"
},
{
"type": "WEB",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-27139"
},
{
"type": "WEB",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-27142"
},
{
"type": "WEB",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-33186"
}
],
"related": [],
"schema_version": "1.7.3",
"summary": "Security fixes for CVE-2026-25679, CVE-2026-27139, CVE-2026-27142, CVE-2026-33186, ghsa-527x-5wrf-22m2, ghsa-9h8m-3fm2-qjrq, ghsa-c9v3-4pv7-87pr, ghsa-h75p-j8xm-m278, ghsa-p77j-4mvh-x3m3 applied in versions: 1.26.7-r0, 1.26.7-r1, 1.26.7-r2",
"upstream": [
"CVE-2026-25679",
"CVE-2026-27139",
"CVE-2026-27142",
"CVE-2026-33186",
"ghsa-527x-5wrf-22m2",
"ghsa-9h8m-3fm2-qjrq",
"ghsa-c9v3-4pv7-87pr",
"ghsa-h75p-j8xm-m278",
"ghsa-p77j-4mvh-x3m3"
]
}
CVE-2026-33186 (GCVE-0-2026-33186)
Vulnerability from cvelistv5 – Published: 2026-03-20 22:23 – Updated: 2026-03-24 18:09
VLAI?
EPSS
Title
gRPC-Go has an authorization bypass via missing leading slash in :path
Summary
gRPC-Go is the Go language implementation of gRPC. Versions prior to 1.79.3 have an authorization bypass resulting from improper input validation of the HTTP/2 `:path` pseudo-header. The gRPC-Go server was too lenient in its routing logic, accepting requests where the `:path` omitted the mandatory leading slash (e.g., `Service/Method` instead of `/Service/Method`). While the server successfully routed these requests to the correct handler, authorization interceptors (including the official `grpc/authz` package) evaluated the raw, non-canonical path string. Consequently, "deny" rules defined using canonical paths (starting with `/`) failed to match the incoming request, allowing it to bypass the policy if a fallback "allow" rule was present. This affects gRPC-Go servers that use path-based authorization interceptors, such as the official RBAC implementation in `google.golang.org/grpc/authz` or custom interceptors relying on `info.FullMethod` or `grpc.Method(ctx)`; AND that have a security policy contains specific "deny" rules for canonical paths but allows other requests by default (a fallback "allow" rule). The vulnerability is exploitable by an attacker who can send raw HTTP/2 frames with malformed `:path` headers directly to the gRPC server. The fix in version 1.79.3 ensures that any request with a `:path` that does not start with a leading slash is immediately rejected with a `codes.Unimplemented` error, preventing it from reaching authorization interceptors or handlers with a non-canonical path string. While upgrading is the most secure and recommended path, users can mitigate the vulnerability using one of the following methods: Use a validating interceptor (recommended mitigation); infrastructure-level normalization; and/or policy hardening.
Severity ?
9.1 (Critical)
CWE
- CWE-285 - Improper Authorization
Assigner
References
| URL | Tags | ||||
|---|---|---|---|---|---|
|
|||||
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CVE-2026-27142 (GCVE-0-2026-27142)
Vulnerability from cvelistv5 – Published: 2026-03-06 21:28 – Updated: 2026-03-16 15:21
VLAI?
EPSS
Title
URLs in meta content attribute actions are not escaped in html/template
Summary
Actions which insert URLs into the content attribute of HTML meta tags are not escaped. This can allow XSS if the meta tag also has an http-equiv attribute with the value "refresh". A new GODEBUG setting has been added, htmlmetacontenturlescape, which can be used to disable escaping URLs in actions in the meta content attribute which follow "url=" by setting htmlmetacontenturlescape=0.
Severity ?
6.1 (Medium)
CWE
- CWE-79 - Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Assigner
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Go standard library | html/template |
Affected:
0 , < 1.25.8
(semver)
Affected: 1.26.0-0 , < 1.26.1 (semver) |
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"url": "https://go.dev/cl/752081"
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CVE-2026-25679 (GCVE-0-2026-25679)
Vulnerability from cvelistv5 – Published: 2026-03-06 21:28 – Updated: 2026-03-10 13:37
VLAI?
EPSS
Title
Incorrect parsing of IPv6 host literals in net/url
Summary
url.Parse insufficiently validated the host/authority component and accepted some invalid URLs.
Severity ?
7.5 (High)
CWE
- CWE-1286 - Improper Validation of Syntactic Correctness of Input
Assigner
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Go standard library | net/url |
Affected:
0 , < 1.25.8
(semver)
Affected: 1.26.0-0 , < 1.26.1 (semver) |
Credits
Masaki Hara (https://github.com/qnighy) of Wantedly
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CVE-2026-27139 (GCVE-0-2026-27139)
Vulnerability from cvelistv5 – Published: 2026-03-06 21:28 – Updated: 2026-03-09 14:53
VLAI?
EPSS
Title
FileInfo can escape from a Root in os
Summary
On Unix platforms, when listing the contents of a directory using File.ReadDir or File.Readdir the returned FileInfo could reference a file outside of the Root in which the File was opened. The impact of this escape is limited to reading metadata provided by lstat from arbitrary locations on the filesystem without permitting reading or writing files outside the root.
Severity ?
CWE
- CWE-363 - Race Condition Enabling Link Following
Assigner
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Go standard library | os |
Affected:
0 , < 1.25.8
(semver)
Affected: 1.26.0-0 , < 1.26.1 (semver) |
Credits
Miloslav Trmač of Red Hat
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],
"title": "FileInfo can escape from a Root in os"
}
},
"cveMetadata": {
"assignerOrgId": "1bb62c36-49e3-4200-9d77-64a1400537cc",
"assignerShortName": "Go",
"cveId": "CVE-2026-27139",
"datePublished": "2026-03-06T21:28:14.451Z",
"dateReserved": "2026-02-17T19:57:28.435Z",
"dateUpdated": "2026-03-09T14:53:58.363Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
GHSA-9H8M-3FM2-QJRQ
Vulnerability from github – Published: 2026-02-02 20:07 – Updated: 2026-02-27 21:39
VLAI?
Summary
OpenTelemetry Go SDK Vulnerable to Arbitrary Code Execution via PATH Hijacking
Details
Impact
The OpenTelemetry Go SDK in version v1.20.0-1.39.0 is vulnerable to Path Hijacking (Untrusted Search Paths) on macOS/Darwin systems. The resource detection code in sdk/resource/host_id.go executes the ioreg system command using a search path. An attacker with the ability to locally modify the PATH environment variable can achieve Arbitrary Code Execution (ACE) within the context of the application.
Patches
This has been patched in d45961b, which was released with v1.40.0.
References
Severity ?
7.0 (High)
{
"affected": [
{
"package": {
"ecosystem": "Go",
"name": "go.opentelemetry.io/otel/sdk"
},
"ranges": [
{
"events": [
{
"introduced": "1.21.0"
},
{
"fixed": "1.40.0"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-24051"
],
"database_specific": {
"cwe_ids": [
"CWE-426"
],
"github_reviewed": true,
"github_reviewed_at": "2026-02-02T20:07:46Z",
"nvd_published_at": "2026-02-02T23:16:07Z",
"severity": "HIGH"
},
"details": "### Impact\nThe OpenTelemetry Go SDK in version `v1.20.0`-`1.39.0` is vulnerable to Path Hijacking (Untrusted Search Paths) on macOS/Darwin systems. The resource detection code in `sdk/resource/host_id.go` executes the `ioreg` system command using a search path. An attacker with the ability to locally modify the PATH environment variable can achieve Arbitrary Code Execution (ACE) within the context of the application.\n\n### Patches\nThis has been patched in [d45961b](https://github.com/open-telemetry/opentelemetry-go/commit/d45961bcda453fcbdb6469c22d6e88a1f9970a53), which was released with `v1.40.0`.\n\n### References\n- [CWE-426: Untrusted Search Path](https://cwe.mitre.org/data/definitions/426.html)",
"id": "GHSA-9h8m-3fm2-qjrq",
"modified": "2026-02-27T21:39:46Z",
"published": "2026-02-02T20:07:46Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/open-telemetry/opentelemetry-go/security/advisories/GHSA-9h8m-3fm2-qjrq"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-24051"
},
{
"type": "WEB",
"url": "https://github.com/open-telemetry/opentelemetry-go/commit/d45961bcda453fcbdb6469c22d6e88a1f9970a53"
},
{
"type": "PACKAGE",
"url": "https://github.com/open-telemetry/opentelemetry-go"
},
{
"type": "WEB",
"url": "https://pkg.go.dev/vuln/GO-2026-4394"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
],
"summary": "OpenTelemetry Go SDK Vulnerable to Arbitrary Code Execution via PATH Hijacking"
}
GHSA-527X-5WRF-22M2
Vulnerability from github – Published: 2026-01-08 20:12 – Updated: 2026-01-08 20:12
VLAI?
Summary
CoreDNS gRPC/HTTPS/HTTP3 servers lack resource limits, enabling DoS via unbounded connections and oversized messages
Details
Multiple CoreDNS server implementations (gRPC, HTTPS, and HTTP/3) lack critical resource-limiting controls. An unauthenticated remote attacker can exhaust memory and degrade or crash the server by opening many concurrent connections, streams, or sending oversized request bodies. The issue is similar in nature to CVE-2025-47950 (QUIC DoS) but affects additional server types that do not enforce connection limits, stream limits, or message size constraints.
Impact
1. Missing connection and stream limits (gRPC / HTTPS / HTTP3)
The affected servers do not enforce reasonable upper bounds on concurrent connections or active streams. An attacker can:
- Open many parallel connections
- Rapidly issue requests without limit
- Consume memory until the CoreDNS process becomes unresponsive or is terminated by the OOM killer
Testing demonstrates that modest resource configurations (e.g., 256 MB RAM) can be exhausted quickly. Increasing concurrency parameters in the PoCs allows attackers to scale the impact.
2. Missing message-size validation in the gRPC server
The gRPC server accepts arbitrarily large protobuf messages (default limit ~4 MB per request) without validating against DNS protocol constraints (maximum 64 KB). Sending multiple concurrent oversized messages can quickly exhaust available memory.
This vulnerability mirrors earlier hardening work in PR https://github.com/coredns/coredns/pull/7490, which applied checks for upstream proxying but left server-side request validation unprotected.
Result:
In all cases, remote unauthenticated attackers can reliably trigger memory exhaustion and cause a denial of service.
Patches
v1.14.0
Severity ?
{
"affected": [
{
"package": {
"ecosystem": "Go",
"name": "github.com/coredns/coredns"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "1.14.0"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2025-68151"
],
"database_specific": {
"cwe_ids": [
"CWE-770"
],
"github_reviewed": true,
"github_reviewed_at": "2026-01-08T20:12:58Z",
"nvd_published_at": "2026-01-08T16:15:59Z",
"severity": "MODERATE"
},
"details": "Multiple CoreDNS server implementations (gRPC, HTTPS, and HTTP/3) lack critical resource-limiting controls. An unauthenticated remote attacker can exhaust memory and degrade or crash the server by opening many concurrent connections, streams, or sending oversized request bodies. The issue is similar in nature to CVE-2025-47950 (QUIC DoS) but affects additional server types that do not enforce connection limits, stream limits, or message size constraints.\n\n### Impact\n\n#### 1. Missing connection and stream limits (gRPC / HTTPS / HTTP3)\n\nThe affected servers do not enforce reasonable upper bounds on concurrent connections or active streams. An attacker can:\n\n- Open many parallel connections\n- Rapidly issue requests without limit\n- Consume memory until the CoreDNS process becomes unresponsive or is terminated by the OOM killer\n\nTesting demonstrates that modest resource configurations (e.g., 256 MB RAM) can be exhausted quickly. Increasing concurrency parameters in the PoCs allows attackers to scale the impact.\n\n#### 2. Missing message-size validation in the gRPC server\n\nThe gRPC server accepts arbitrarily large protobuf messages (default limit ~4 MB per request) without validating against DNS protocol constraints (maximum 64 KB). Sending multiple concurrent oversized messages can quickly exhaust available memory.\n\nThis vulnerability mirrors earlier hardening work in PR https://github.com/coredns/coredns/pull/7490, which applied checks for upstream proxying but left server-side request validation unprotected.\n\n#### Result:\nIn all cases, remote unauthenticated attackers can reliably trigger memory exhaustion and cause a denial of service.\n\n\n### Patches\n_v1.14.0_",
"id": "GHSA-527x-5wrf-22m2",
"modified": "2026-01-08T20:12:58Z",
"published": "2026-01-08T20:12:58Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/coredns/coredns/security/advisories/GHSA-527x-5wrf-22m2"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-68151"
},
{
"type": "WEB",
"url": "https://github.com/coredns/coredns/pull/7490"
},
{
"type": "WEB",
"url": "https://github.com/coredns/coredns/commit/0d8cbb1a6bcb6bc9c1a489865278b8725fa20812"
},
{
"type": "PACKAGE",
"url": "https://github.com/coredns/coredns"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U",
"type": "CVSS_V4"
}
],
"summary": "CoreDNS gRPC/HTTPS/HTTP3 servers lack resource limits, enabling DoS via unbounded connections and oversized messages"
}
GHSA-C9V3-4PV7-87PR
Vulnerability from github – Published: 2026-03-06 18:04 – Updated: 2026-03-06 22:43
VLAI?
Summary
CoreDNS ACL Bypass
Details
A logical vulnerability in CoreDNS allows DNS access controls to be bypassed due to the default execution order of plugins. Security plugins such as acl are evaluated before the rewrite plugin, resulting in a Time-of-Check Time-of-Use (TOCTOU) flaw.
Impact
In multi-tenant Kubernetes clusters, this flaw undermines DNS-based segmentation strategies.
Example scenario: 1. ACL blocks access to *.admin.svc.cluster.local 2. A rewrite rule maps public-name → admin.svc.cluster.local 3. An unprivileged pod queries public-name 4. ACL allows the request 5. Rewrite exposes the internal admin service IP
This allows unauthorized service discovery and reconnaissance of restricted internal infrastructure.
Patches
Has the problem been patched? What versions should users upgrade to?
Workarounds
- Reorder the default plugin.cfg so that:
- rewrite and other normalization plugins run before acl, opa, and firewall
- Ensure all access control checks are applied after name normalization.
Severity ?
7.7 (High)
{
"affected": [
{
"package": {
"ecosystem": "Go",
"name": "github.com/coredns/coredns"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "1.14.2"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-26017"
],
"database_specific": {
"cwe_ids": [
"CWE-367"
],
"github_reviewed": true,
"github_reviewed_at": "2026-03-06T18:04:00Z",
"nvd_published_at": "2026-03-06T16:16:10Z",
"severity": "HIGH"
},
"details": "A logical vulnerability in CoreDNS allows DNS access controls to be bypassed due to the default execution order of plugins. Security plugins such as acl are evaluated before the rewrite plugin, resulting in a Time-of-Check Time-of-Use (TOCTOU) flaw.\n\n\n### Impact\n\nIn multi-tenant Kubernetes clusters, this flaw undermines DNS-based segmentation strategies.\n\nExample scenario:\n1. ACL blocks access to *.admin.svc.cluster.local\n2. A rewrite rule maps public-name \u2192 admin.svc.cluster.local\n3. An unprivileged pod queries public-name\n4. ACL allows the request\n5. Rewrite exposes the internal admin service IP\n\nThis allows unauthorized service discovery and reconnaissance of restricted internal infrastructure.\n\n### Patches\n_Has the problem been patched? What versions should users upgrade to?_\n\n### Workarounds\n\n- Reorder the default plugin.cfg so that:\n - rewrite and other normalization plugins run before acl, opa, and firewall\n- Ensure all access control checks are applied after name normalization.",
"id": "GHSA-c9v3-4pv7-87pr",
"modified": "2026-03-06T22:43:40Z",
"published": "2026-03-06T18:04:00Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/coredns/coredns/security/advisories/GHSA-c9v3-4pv7-87pr"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-26017"
},
{
"type": "PACKAGE",
"url": "https://github.com/coredns/coredns"
},
{
"type": "WEB",
"url": "https://github.com/coredns/coredns/releases/tag/v1.14.2"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N",
"type": "CVSS_V3"
}
],
"summary": "CoreDNS ACL Bypass"
}
GHSA-H75P-J8XM-M278
Vulnerability from github – Published: 2026-03-06 22:08 – Updated: 2026-03-06 22:08
VLAI?
Summary
CoreDNS Loop Detection Denial of Service Vulnerability
Details
Executive Summary
A Denial of Service vulnerability exists in CoreDNS's loop detection plugin that allows an attacker to crash the DNS server by sending specially crafted DNS queries. The vulnerability stems from the use of a predictable pseudo-random number generator (PRNG) for generating a secret query name, combined with a fatal error handler that terminates the entire process.
Technical Details
Vulnerability Description
The CoreDNS loop plugin is designed to detect forwarding loops by performing a self-test during server startup. The plugin generates a random query name (qname) using Go's math/rand package and sends an HINFO query to itself. If the server receives multiple matching queries, it assumes a forwarding loop exists and terminates.
The vulnerability arises from two design flaws:
-
Predictable PRNG Seed: The random number generator is seeded with
time.Now().UnixNano(), making the generated qname predictable if an attacker knows the approximate server start time. -
Fatal Error Handler: When the plugin detects what it believes is a loop (3+ matching HINFO queries), it calls
log.Fatalf()which invokesos.Exit(1), immediately terminating the process without cleanup or recovery.
Affected Code
File: plugin/loop/setup.go
// PRNG seeded with predictable timestamp
var r = rand.New(time.Now().UnixNano())
// Qname generation using two consecutive PRNG calls
func qname(zone string) string {
l1 := strconv.Itoa(r.Int())
l2 := strconv.Itoa(r.Int())
return dnsutil.Join(l1, l2, zone)
}
File: plugin/loop/loop.go
func (l *Loop) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
// ... validation checks ...
if state.Name() == l.qname {
l.inc() // Increment counter
}
if l.seen() > 2 {
// FATAL: Terminates entire process
log.Fatalf("Loop (%s -> %s) detected for zone %q...", ...)
}
// ...
}
File: plugin/pkg/log/log.go
func Fatalf(format string, v ...any) {
logf(fatal, format, v...)
os.Exit(1) // Immediate process termination
}
Exploitation Window
The loop plugin remains active during the following conditions:
| Condition | Window Duration | Attack Feasibility |
|---|---|---|
| Healthy startup | 2 seconds | Requires precise timing |
| Self-test failure (upstream unreachable) | 30 seconds | HIGH - Extended window |
| Network degradation | Variable | Depends on retry behavior |
Attack Scenario
Primary Attack Vector: Network Degradation
When the upstream DNS server is unreachable (network partition, misconfiguration, outage), the loop plugin's self-test fails repeatedly. During this period:
- The loop plugin remains active for up to 30 seconds
- Each self-test attempt generates an HINFO query visible in CoreDNS logs
- An attacker with log access (shared Kubernetes cluster, centralized logging) can observe the qname
- The attacker sends 3 HINFO queries with the observed qname
- The server immediately crashes
┌──────────────────────────────────────────────────────────────────────────┐
│ ATTACK TIMELINE │
├──────────────────────────────────────────────────────────────────────────┤
│ T+0s CoreDNS starts, PRNG seeded with UnixNano() │
│ T+0.5s Self-test HINFO query sent (visible in logs) │
│ T+2s Self-test fails (upstream timeout) │
│ T+3s Retry #1 - counter resets, qname unchanged │
│ T+5s Retry #2 - attacker observes qname in logs │
│ T+5.1s ATTACKER: Send HINFO #1 → counter = 1 │
│ T+5.2s ATTACKER: Send HINFO #2 → counter = 2 │
│ T+5.3s ATTACKER: Send HINFO #3 → counter = 3 → os.Exit(1) │
│ T+5.3s SERVER CRASHES │
└──────────────────────────────────────────────────────────────────────────┘
Impact Assessment
Attack Requirements
| Requirement | Notes |
|---|---|
| Network Access | Must be able to send UDP packets to CoreDNS port |
| Log Access | Required to observe the qname (common in shared clusters) |
| Timing | Extended window during network degradation |
| Authentication | None required |
Real-World Impact
CoreDNS is the default DNS server for Kubernetes clusters. A successful attack would:
- Disruption: All DNS resolution fails within the cluster
- Cascading Failures: Services unable to discover each other
- Restart Loop: If attack persists, CoreDNS enters crash-restart cycle
- Data Plane Impact: Application-level failures across the cluster
References
- CoreDNS GitHub: https://github.com/coredns/coredns
- Loop Plugin Documentation: https://coredns.io/plugins/loop/
- Go math/rand Documentation: https://pkg.go.dev/math/rand
Severity ?
7.5 (High)
{
"affected": [
{
"package": {
"ecosystem": "Go",
"name": "github.com/coredns/coredns"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "1.14.2"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-26018"
],
"database_specific": {
"cwe_ids": [
"CWE-337"
],
"github_reviewed": true,
"github_reviewed_at": "2026-03-06T22:08:22Z",
"nvd_published_at": "2026-03-06T16:16:10Z",
"severity": "HIGH"
},
"details": "## Executive Summary\n\nA Denial of Service vulnerability exists in CoreDNS\u0027s loop detection plugin that allows an attacker to crash the DNS server by sending specially crafted DNS queries. The vulnerability stems from the use of a predictable pseudo-random number generator (PRNG) for generating a secret query name, combined with a fatal error handler that terminates the entire process.\n\n---\n## Technical Details\n\n### Vulnerability Description\n\nThe CoreDNS `loop` plugin is designed to detect forwarding loops by performing a self-test during server startup. The plugin generates a random query name (`qname`) using Go\u0027s `math/rand` package and sends an HINFO query to itself. If the server receives multiple matching queries, it assumes a forwarding loop exists and terminates.\n\n**The vulnerability arises from two design flaws:**\n\n1. **Predictable PRNG Seed**: The random number generator is seeded with `time.Now().UnixNano()`, making the generated qname predictable if an attacker knows the approximate server start time.\n\n2. **Fatal Error Handler**: When the plugin detects what it believes is a loop (3+ matching HINFO queries), it calls `log.Fatalf()` which invokes `os.Exit(1)`, immediately terminating the process without cleanup or recovery.\n\n### Affected Code\n\n**File: `plugin/loop/setup.go`**\n```go\n// PRNG seeded with predictable timestamp\nvar r = rand.New(time.Now().UnixNano())\n\n// Qname generation using two consecutive PRNG calls\nfunc qname(zone string) string {\n l1 := strconv.Itoa(r.Int())\n l2 := strconv.Itoa(r.Int())\n return dnsutil.Join(l1, l2, zone)\n}\n```\n\n**File: `plugin/loop/loop.go`**\n```go\nfunc (l *Loop) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {\n // ... validation checks ...\n \n if state.Name() == l.qname {\n l.inc() // Increment counter\n }\n\n if l.seen() \u003e 2 {\n // FATAL: Terminates entire process\n log.Fatalf(\"Loop (%s -\u003e %s) detected for zone %q...\", ...)\n }\n \n // ...\n}\n```\n\n**File: `plugin/pkg/log/log.go`**\n```go\nfunc Fatalf(format string, v ...any) {\n logf(fatal, format, v...)\n os.Exit(1) // Immediate process termination\n}\n```\n\n### Exploitation Window\n\nThe loop plugin remains active during the following conditions:\n\n| Condition | Window Duration | Attack Feasibility |\n|-----------|-----------------|-------------------|\n| Healthy startup | 2 seconds | Requires precise timing |\n| Self-test failure (upstream unreachable) | 30 seconds | **HIGH** - Extended window |\n| Network degradation | Variable | Depends on retry behavior |\n\n### Attack Scenario\n\n**Primary Attack Vector: Network Degradation**\n\nWhen the upstream DNS server is unreachable (network partition, misconfiguration, outage), the loop plugin\u0027s self-test fails repeatedly. During this period:\n\n1. The loop plugin remains active for up to 30 seconds\n2. Each self-test attempt generates an HINFO query visible in CoreDNS logs\n3. An attacker with log access (shared Kubernetes cluster, centralized logging) can observe the qname\n4. The attacker sends 3 HINFO queries with the observed qname\n5. The server immediately crashes\n\n```\n\u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510\n\u2502 ATTACK TIMELINE \u2502\n\u251c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2524\n\u2502 T+0s CoreDNS starts, PRNG seeded with UnixNano() \u2502\n\u2502 T+0.5s Self-test HINFO query sent (visible in logs) \u2502\n\u2502 T+2s Self-test fails (upstream timeout) \u2502\n\u2502 T+3s Retry #1 - counter resets, qname unchanged \u2502\n\u2502 T+5s Retry #2 - attacker observes qname in logs \u2502\n\u2502 T+5.1s ATTACKER: Send HINFO #1 \u2192 counter = 1 \u2502\n\u2502 T+5.2s ATTACKER: Send HINFO #2 \u2192 counter = 2 \u2502\n\u2502 T+5.3s ATTACKER: Send HINFO #3 \u2192 counter = 3 \u2192 os.Exit(1) \u2502\n\u2502 T+5.3s SERVER CRASHES \u2502\n\u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518\n```\n\n---\n\n## Impact Assessment\n\n### Attack Requirements\n\n| Requirement | Notes |\n|-------------|-------|\n| Network Access | Must be able to send UDP packets to CoreDNS port |\n| Log Access | Required to observe the qname (common in shared clusters) |\n| Timing | Extended window during network degradation |\n| Authentication | None required |\n\n### Real-World Impact\n\nCoreDNS is the default DNS server for Kubernetes clusters. A successful attack would:\n\n1. **Disruption**: All DNS resolution fails within the cluster\n2. **Cascading Failures**: Services unable to discover each other\n3. **Restart Loop**: If attack persists, CoreDNS enters crash-restart cycle\n4. **Data Plane Impact**: Application-level failures across the cluster\n\n## References\n\n- CoreDNS GitHub: https://github.com/coredns/coredns\n- Loop Plugin Documentation: https://coredns.io/plugins/loop/\n- Go math/rand Documentation: https://pkg.go.dev/math/rand",
"id": "GHSA-h75p-j8xm-m278",
"modified": "2026-03-06T22:08:22Z",
"published": "2026-03-06T22:08:22Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/coredns/coredns/security/advisories/GHSA-h75p-j8xm-m278"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-26018"
},
{
"type": "PACKAGE",
"url": "https://github.com/coredns/coredns"
},
{
"type": "WEB",
"url": "https://github.com/coredns/coredns/releases/tag/v1.14.2"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
],
"summary": "CoreDNS Loop Detection Denial of Service Vulnerability"
}
GHSA-P77J-4MVH-X3M3
Vulnerability from github – Published: 2026-03-18 20:10 – Updated: 2026-03-25 18:12
VLAI?
Summary
gRPC-Go has an authorization bypass via missing leading slash in :path
Details
Impact
What kind of vulnerability is it? Who is impacted?
It is an Authorization Bypass resulting from Improper Input Validation of the HTTP/2 :path pseudo-header.
The gRPC-Go server was too lenient in its routing logic, accepting requests where the :path omitted the mandatory leading slash (e.g., Service/Method instead of /Service/Method). While the server successfully routed these requests to the correct handler, authorization interceptors (including the official grpc/authz package) evaluated the raw, non-canonical path string. Consequently, "deny" rules defined using canonical paths (starting with /) failed to match the incoming request, allowing it to bypass the policy if a fallback "allow" rule was present.
Who is impacted?
This affects gRPC-Go servers that meet both of the following criteria:
1. They use path-based authorization interceptors, such as the official RBAC implementation in google.golang.org/grpc/authz or custom interceptors relying on info.FullMethod or grpc.Method(ctx).
2. Their security policy contains specific "deny" rules for canonical paths but allows other requests by default (a fallback "allow" rule).
The vulnerability is exploitable by an attacker who can send raw HTTP/2 frames with malformed :path headers directly to the gRPC server.
Patches
Has the problem been patched? What versions should users upgrade to?
Yes, the issue has been patched. The fix ensures that any request with a :path that does not start with a leading slash is immediately rejected with a codes.Unimplemented error, preventing it from reaching authorization interceptors or handlers with a non-canonical path string.
Users should upgrade to the following versions (or newer): * v1.79.3 * The latest master branch.
It is recommended that all users employing path-based authorization (especially grpc/authz) upgrade as soon as the patch is available in a tagged release.
Workarounds
Is there a way for users to fix or remediate the vulnerability without upgrading?
While upgrading is the most secure and recommended path, users can mitigate the vulnerability using one of the following methods:
1. Use a Validating Interceptor (Recommended Mitigation)
Add an "outermost" interceptor to your server that validates the path before any other authorization logic runs:
func pathValidationInterceptor(ctx context.Context, req any, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (any, error) {
if info.FullMethod == "" || info.FullMethod[0] != '/' {
return nil, status.Errorf(codes.Unimplemented, "malformed method name")
}
return handler(ctx, req)
}
// Ensure this is the FIRST interceptor in your chain
s := grpc.NewServer(
grpc.ChainUnaryInterceptor(pathValidationInterceptor, authzInterceptor),
)
2. Infrastructure-Level Normalization
If your gRPC server is behind a reverse proxy or load balancer (such as Envoy, NGINX, or an L7 Cloud Load Balancer), ensure it is configured to enforce strict HTTP/2 compliance for pseudo-headers and reject or normalize requests where the :path header does not start with a leading slash.
3. Policy Hardening
Switch to a "default deny" posture in your authorization policies (explicitly listing all allowed paths and denying everything else) to reduce the risk of bypasses via malformed inputs.
Severity ?
9.1 (Critical)
{
"affected": [
{
"package": {
"ecosystem": "Go",
"name": "google.golang.org/grpc"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "1.79.3"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-33186"
],
"database_specific": {
"cwe_ids": [
"CWE-285"
],
"github_reviewed": true,
"github_reviewed_at": "2026-03-18T20:10:29Z",
"nvd_published_at": "2026-03-20T23:16:45Z",
"severity": "CRITICAL"
},
"details": "### Impact\n_What kind of vulnerability is it? Who is impacted?_\n\nIt is an **Authorization Bypass** resulting from **Improper Input Validation** of the HTTP/2 `:path` pseudo-header.\n\nThe gRPC-Go server was too lenient in its routing logic, accepting requests where the `:path` omitted the mandatory leading slash (e.g., `Service/Method` instead of `/Service/Method`). While the server successfully routed these requests to the correct handler, authorization interceptors (including the official `grpc/authz` package) evaluated the raw, non-canonical path string. Consequently, \"deny\" rules defined using canonical paths (starting with `/`) failed to match the incoming request, allowing it to bypass the policy if a fallback \"allow\" rule was present.\n\n**Who is impacted?**\nThis affects gRPC-Go servers that meet both of the following criteria:\n1. They use path-based authorization interceptors, such as the official RBAC implementation in `google.golang.org/grpc/authz` or custom interceptors relying on `info.FullMethod` or `grpc.Method(ctx)`.\n2. Their security policy contains specific \"deny\" rules for canonical paths but allows other requests by default (a fallback \"allow\" rule).\n\nThe vulnerability is exploitable by an attacker who can send raw HTTP/2 frames with malformed `:path` headers directly to the gRPC server.\n\n### Patches\n_Has the problem been patched? What versions should users upgrade to?_\n\nYes, the issue has been patched. The fix ensures that any request with a `:path` that does not start with a leading slash is immediately rejected with a `codes.Unimplemented` error, preventing it from reaching authorization interceptors or handlers with a non-canonical path string.\n\nUsers should upgrade to the following versions (or newer):\n* **v1.79.3**\n* The latest **master** branch.\n\nIt is recommended that all users employing path-based authorization (especially `grpc/authz`) upgrade as soon as the patch is available in a tagged release.\n\n### Workarounds\n_Is there a way for users to fix or remediate the vulnerability without upgrading?_\n\nWhile upgrading is the most secure and recommended path, users can mitigate the vulnerability using one of the following methods:\n\n#### 1. Use a Validating Interceptor (Recommended Mitigation)\nAdd an \"outermost\" interceptor to your server that validates the path before any other authorization logic runs:\n\n```go\nfunc pathValidationInterceptor(ctx context.Context, req any, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (any, error) {\n if info.FullMethod == \"\" || info.FullMethod[0] != \u0027/\u0027 {\n return nil, status.Errorf(codes.Unimplemented, \"malformed method name\")\n } \n return handler(ctx, req)\n}\n\n// Ensure this is the FIRST interceptor in your chain\ns := grpc.NewServer(\n grpc.ChainUnaryInterceptor(pathValidationInterceptor, authzInterceptor),\n)\n```\n\n#### 2. Infrastructure-Level Normalization\nIf your gRPC server is behind a reverse proxy or load balancer (such as Envoy, NGINX, or an L7 Cloud Load Balancer), ensure it is configured to enforce strict HTTP/2 compliance for pseudo-headers and reject or normalize requests where the `:path` header does not start with a leading slash.\n\n#### 3. Policy Hardening\nSwitch to a \"default deny\" posture in your authorization policies (explicitly listing all allowed paths and denying everything else) to reduce the risk of bypasses via malformed inputs.",
"id": "GHSA-p77j-4mvh-x3m3",
"modified": "2026-03-25T18:12:09Z",
"published": "2026-03-18T20:10:29Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/grpc/grpc-go/security/advisories/GHSA-p77j-4mvh-x3m3"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-33186"
},
{
"type": "PACKAGE",
"url": "https://github.com/grpc/grpc-go"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N",
"type": "CVSS_V3"
}
],
"summary": "gRPC-Go has an authorization bypass via missing leading slash in :path"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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