Vulnerability-Lookup

GHSA-WXRW-GVG8-FQJP

Vulnerability from github – Published: 2026-02-06 22:52 – Updated: 2026-02-09 22:39

Summary

Sliver has DNS C2 OTP Bypass that Allows Unauthenticated Session Flooding and Denial of Service

Details

Summary

The DNS C2 listener accepts unauthenticated TOTP bootstrap messages and allocates server-side DNS sessions without validating OTP values, even when EnforceOTP is enabled. Because sessions are stored without a cleanup/expiry path in this flow, an unauthenticated remote actor can repeatedly create sessions and drive memory exhaustion.

Vulnerable Component

server/c2/dns.go:84-90 (EnforceOTP stored but not enforced in bootstrap)
server/c2/dns.go:378-390 (TOTP requests routed directly to bootstrap)
server/c2/dns.go:490-521 (handleHello allocates session without OTP validation)
server/c2/dns.go:495 (sessions.Store with no lifecycle control in this path)
client/command/jobs/dns.go:46-52 (operator-facing EnforceOTP control implies auth gate)
implant/sliver/transports/dnsclient/dnsclient.go:896-900 (otpMsg sends TOTP with ID=0)
protobuf/dnspb/dns.proto:22 (documents TOTP in ID field)

Attack Vector

Network-accessible DNS listener
No authentication required
Low-complexity repeated DNS query loop
Trigger path: DNSMessageType_TOTP bootstrap handling

Proof of Concept

Preconditions

DNS listener is reachable
DNS C2 job is active

Reproduction Steps

Send repeated DNS queries with a minimal protobuf message of type TOTP.
Observe repeated session allocation/issuance behavior.
Continue requests to increase active in-memory session state.

Example

while true; do
  dig +short @<DNS_C2_IP> baa8.<parent-domain> A >/dev/null
done

baa8 is a base32 payload for a minimal TOTP-type protobuf message.

Observable Indicators

Repeated bootstrap/session-allocation log entries from handleHello
Rising memory usage in the Sliver server process
Service slowdown or instability under sustained request volume

Impact

Unauthenticated remote denial of service (availability)
Resource exhaustion through unbounded session growth in DNS bootstrap path
Estimated CVSS v3.1: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H (7.5 High)

Severity ?

7.5 (High)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 1.6.11"
      },
      "package": {
        "ecosystem": "Go",
        "name": "github.com/bishopfox/sliver"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.6.12"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-25791"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-306",
      "CWE-400"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-02-06T22:52:00Z",
    "nvd_published_at": "2026-02-09T21:15:49Z",
    "severity": "HIGH"
  },
  "details": "## Summary\nThe DNS C2 listener accepts unauthenticated `TOTP` bootstrap messages and allocates server-side DNS sessions without validating OTP values, even when `EnforceOTP` is enabled. Because sessions are stored without a cleanup/expiry path in this flow, an unauthenticated remote actor can repeatedly create sessions and drive memory exhaustion.\n\n## Vulnerable Component\n- `server/c2/dns.go:84-90` (`EnforceOTP` stored but not enforced in bootstrap)\n- `server/c2/dns.go:378-390` (`TOTP` requests routed directly to bootstrap)\n- `server/c2/dns.go:490-521` (`handleHello` allocates session without OTP validation)\n- `server/c2/dns.go:495` (`sessions.Store` with no lifecycle control in this path)\n- `client/command/jobs/dns.go:46-52` (operator-facing `EnforceOTP` control implies auth gate)\n- `implant/sliver/transports/dnsclient/dnsclient.go:896-900` (`otpMsg` sends `TOTP` with `ID=0`)\n- `protobuf/dnspb/dns.proto:22` (documents TOTP in `ID` field)\n\n## Attack Vector\n- Network-accessible DNS listener\n- No authentication required\n- Low-complexity repeated DNS query loop\n- Trigger path: `DNSMessageType_TOTP` bootstrap handling\n\n## Proof of Concept\n### Preconditions\n- DNS listener is reachable\n- DNS C2 job is active\n\n### Reproduction Steps\n1. Send repeated DNS queries with a minimal protobuf message of type `TOTP`.\n2. Observe repeated session allocation/issuance behavior.\n3. Continue requests to increase active in-memory session state.\n\n### Example\n```bash\nwhile true; do\n  dig +short @\u003cDNS_C2_IP\u003e baa8.\u003cparent-domain\u003e A \u003e/dev/null\ndone\n```\n\n`baa8` is a base32 payload for a minimal TOTP-type protobuf message.\n\n### Observable Indicators\n- Repeated bootstrap/session-allocation log entries from `handleHello`\n- Rising memory usage in the Sliver server process\n- Service slowdown or instability under sustained request volume\n\n## Impact\n- Unauthenticated remote denial of service (availability)\n- Resource exhaustion through unbounded session growth in DNS bootstrap path\n- Estimated CVSS v3.1: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H` (**7.5 High**)",
  "id": "GHSA-wxrw-gvg8-fqjp",
  "modified": "2026-02-09T22:39:50Z",
  "published": "2026-02-06T22:52:00Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/BishopFox/sliver/security/advisories/GHSA-wxrw-gvg8-fqjp"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-25791"
    },
    {
      "type": "WEB",
      "url": "https://github.com/BishopFox/sliver/commit/2b65089b27c553e79e69f1067cad1339e4f3d937"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/BishopFox/sliver"
    },
    {
      "type": "WEB",
      "url": "https://github.com/BishopFox/sliver/releases/tag/v1.7.0"
    }
  ],
  "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": "Sliver has DNS C2 OTP Bypass that Allows Unauthenticated Session Flooding and Denial of Service"
}

CVE-2026-25791 (GCVE-0-2026-25791)

Vulnerability from cvelistv5 – Published: 2026-02-09 20:34 – Updated: 2026-02-10 15:59

Title

Sliver has a DNS C2 OTP Bypass Allows Unauthenticated Session Flooding and Denial of Service

Summary

Sliver is a command and control framework that uses a custom Wireguard netstack. Prior to 1.7.0, the DNS C2 listener accepts unauthenticated TOTP bootstrap messages and allocates server-side DNS sessions without validating OTP values, even when EnforceOTP is enabled. Because sessions are stored without a cleanup/expiry path in this flow, an unauthenticated remote actor can repeatedly create sessions and drive memory exhaustion. This vulnerability is fixed in 1.7.0.

Severity ?

7.5 (High)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CWE

CWE-306 - Missing Authentication for Critical Function
CWE-400 - Uncontrolled Resource Consumption

Assigner

GitHub_M

References

URL

Tags

	https://github.com/BishopFox/sliver/security/advi…	x_refsource_CONFIRM
	https://github.com/BishopFox/sliver/releases/tag/v1.7.0	x_refsource_MISC

Impacted products

	Vendor	Product	Version
	BishopFox	sliver	Affected: < 1.7.0

Show details on NVD website

JSON

To clipboard

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        "metrics": [
          {
            "other": {
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                "id": "CVE-2026-25791",
                "options": [
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                    "Exploitation": "none"
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                  },
                  {
                    "Technical Impact": "partial"
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                "role": "CISA Coordinator",
                "timestamp": "2026-02-10T15:39:42.592936Z",
                "version": "2.0.3"
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        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
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        "discovery": "UNKNOWN"
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      "title": "Sliver has a DNS C2 OTP Bypass Allows Unauthenticated Session Flooding and Denial of Service"
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  },
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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.

Detection rules are retrieved from Rulezet.

Action not permitted

GHSA-WXRW-GVG8-FQJP

Summary

Vulnerable Component

Attack Vector

Proof of Concept

Preconditions

Reproduction Steps

Example

Observable Indicators

Impact

CVE-2026-25791 (GCVE-0-2026-25791)

Tags

Sightings

Nomenclature