Vulnerability-Lookup

RHSA-2026:98629

Vulnerability from csaf_redhat - Published: 2026-11-11 13:56 - Updated: 2026-11-12 05:52

Summary

Red Hat Security Advisory: c-ares security update

Severity

Important

Notes

Topic: An update for c-ares is now available for Red Hat Enterprise Linux 10. Red Hat Product Security has rated this update as having a security impact of Important. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available for each vulnerability from the CVE link(s) in the References section.

Details: The c-ares C library defines asynchronous DNS (Domain Name System) requests and provides name resolving API. Security Fix(es): * c-ares: c-ares: Denial of Service via unvalidated DNS header record counts (CVE-2026-69186) * c-ares: c-ares: CPU exhaustion denial of service via unbounded DNS name compression pointer chains (CVE-2026-69184) For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Terms of Use: This content is licensed under the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/). If you distribute this content, or a modified version of it, you must provide attribution to Red Hat Inc. and provide a link to the original.

CVE-2026-69184

A flaw was found in c-ares, an asynchronous resolver library. The 'ares_dns_name_parse()' function does not properly limit the total pointer hops or assembled name length when enforcing backward DNS compression pointers. A remote attacker, operating a malicious DNS server, can send a specially crafted DNS response containing a long descending pointer chain. This can lead to excessive CPU consumption, causing the single-threaded c-ares event loop to stall and resulting in a denial of service for DNS resolution.

7.5 (High)


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

CWE-770 - Allocation of Resources Without Limits or Throttling

Affected products

Fixed 25 products

Product	Version	Remediation
Unresolved product id: AppStream-10.3.Z:c-ares-debuginfo-0:1.34.6-5.el10_3.2.aarch64	—	Vendor Fix fix Workaround
Unresolved product id: AppStream-10.3.Z:c-ares-debuginfo-0:1.34.6-5.el10_3.2.ppc64le	—	Vendor Fix fix Workaround
Unresolved product id: AppStream-10.3.Z:c-ares-debuginfo-0:1.34.6-5.el10_3.2.s390x	—	Vendor Fix fix Workaround
Unresolved product id: AppStream-10.3.Z:c-ares-debuginfo-0:1.34.6-5.el10_3.2.x86_64	—	Vendor Fix fix Workaround
Unresolved product id: AppStream-10.3.Z:c-ares-debugsource-0:1.34.6-5.el10_3.2.aarch64	—	Vendor Fix fix Workaround
Unresolved product id: AppStream-10.3.Z:c-ares-debugsource-0:1.34.6-5.el10_3.2.ppc64le	—	Vendor Fix fix Workaround
Unresolved product id: AppStream-10.3.Z:c-ares-debugsource-0:1.34.6-5.el10_3.2.s390x	—	Vendor Fix fix Workaround
Unresolved product id: AppStream-10.3.Z:c-ares-debugsource-0:1.34.6-5.el10_3.2.x86_64	—	Vendor Fix fix Workaround
Unresolved product id: AppStream-10.3.Z:c-ares-devel-0:1.34.6-5.el10_3.2.aarch64	—	Vendor Fix fix Workaround
Unresolved product id: AppStream-10.3.Z:c-ares-devel-0:1.34.6-5.el10_3.2.ppc64le	—	Vendor Fix fix Workaround
Unresolved product id: AppStream-10.3.Z:c-ares-devel-0:1.34.6-5.el10_3.2.s390x	—	Vendor Fix fix Workaround
Unresolved product id: AppStream-10.3.Z:c-ares-devel-0:1.34.6-5.el10_3.2.x86_64	—	Vendor Fix fix Workaround
Unresolved product id: BaseOS-10.3.Z:c-ares-0:1.34.6-5.el10_3.2.aarch64	—	Vendor Fix fix Workaround
Unresolved product id: BaseOS-10.3.Z:c-ares-0:1.34.6-5.el10_3.2.ppc64le	—	Vendor Fix fix Workaround
Unresolved product id: BaseOS-10.3.Z:c-ares-0:1.34.6-5.el10_3.2.s390x	—	Vendor Fix fix Workaround
Unresolved product id: BaseOS-10.3.Z:c-ares-0:1.34.6-5.el10_3.2.src	—	Vendor Fix fix Workaround
Unresolved product id: BaseOS-10.3.Z:c-ares-0:1.34.6-5.el10_3.2.x86_64	—	Vendor Fix fix Workaround
Unresolved product id: BaseOS-10.3.Z:c-ares-debuginfo-0:1.34.6-5.el10_3.2.aarch64	—	Vendor Fix fix Workaround
Unresolved product id: BaseOS-10.3.Z:c-ares-debuginfo-0:1.34.6-5.el10_3.2.ppc64le	—	Vendor Fix fix Workaround
Unresolved product id: BaseOS-10.3.Z:c-ares-debuginfo-0:1.34.6-5.el10_3.2.s390x	—	Vendor Fix fix Workaround
Unresolved product id: BaseOS-10.3.Z:c-ares-debuginfo-0:1.34.6-5.el10_3.2.x86_64	—	Vendor Fix fix Workaround
Unresolved product id: BaseOS-10.3.Z:c-ares-debugsource-0:1.34.6-5.el10_3.2.aarch64	—	Vendor Fix fix Workaround
Unresolved product id: BaseOS-10.3.Z:c-ares-debugsource-0:1.34.6-5.el10_3.2.ppc64le	—	Vendor Fix fix Workaround
Unresolved product id: BaseOS-10.3.Z:c-ares-debugsource-0:1.34.6-5.el10_3.2.s390x	—	Vendor Fix fix Workaround
Unresolved product id: BaseOS-10.3.Z:c-ares-debugsource-0:1.34.6-5.el10_3.2.x86_64	—	Vendor Fix fix Workaround

Threats

Impact Important

CVE-2026-69186

A flaw was found in c-ares, an asynchronous resolver library. A remote attacker can send a specially crafted DNS response that causes the `ares_dns_parse()` function to trust attacker-controlled record counts without validating if the response contains enough bytes for the claimed records. This can lead to disproportionate heap memory reservation, resulting in a memory-amplification denial of service (DoS) by degrading or denying name resolution.

7.5 (High)


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

CWE-1284 - Improper Validation of Specified Quantity in Input

Affected products

Fixed 25 products, the same list as for CVE-2026-69184

Threats

Impact Important

References

23 references

URL	Category
https://access.redhat.com/errata/RHSA-2026:98629	self
https://access.redhat.com/security/updates/classi…	external
https://bugzilla.redhat.com/show_bug.cgi?id=2538212	external
https://bugzilla.redhat.com/show_bug.cgi?id=2538396	external
https://security.access.redhat.com/data/csaf/v2/a…	self
https://access.redhat.com/security/cve/CVE-2026-69184	self
https://bugzilla.redhat.com/show_bug.cgi?id=2538396	external
https://www.cve.org/CVERecord?id=CVE-2026-69184	external
https://nvd.nist.gov/vuln/detail/CVE-2026-69184	external
https://github.com/c-ares/c-ares/commit/5c8341ba6…	external
https://github.com/c-ares/c-ares/commit/f1288bbc7…	external
https://github.com/c-ares/c-ares/pull/1164	external
https://github.com/c-ares/c-ares/pull/1210	external
https://github.com/c-ares/c-ares/releases/tag/v1.34.7	external
https://github.com/c-ares/c-ares/security/advisor…	external
https://access.redhat.com/security/cve/CVE-2026-69186	self
https://bugzilla.redhat.com/show_bug.cgi?id=2538212	external
https://www.cve.org/CVERecord?id=CVE-2026-69186	external
https://nvd.nist.gov/vuln/detail/CVE-2026-69186	external
https://github.com/c-ares/c-ares/commit/e47c203f9…	external
https://github.com/c-ares/c-ares/commit/eaded4cb2…	external
https://github.com/c-ares/c-ares/pull/1134	external
https://github.com/c-ares/c-ares/security/advisor…	external

JSON

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          "text": "A flaw was found in c-ares, an asynchronous resolver library. The \u0027ares_dns_name_parse()\u0027 function does not properly limit the total pointer hops or assembled name length when enforcing backward DNS compression pointers. A remote attacker, operating a malicious DNS server, can send a specially crafted DNS response containing a long descending pointer chain. This can lead to excessive CPU consumption, causing the single-threaded c-ares event loop to stall and resulting in a denial of service for DNS resolution.",
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          "text": "c-ares: c-ares: CPU exhaustion denial of service via unbounded DNS name compression pointer chains",
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          "text": "A flaw was found in the c-ares asynchronous DNS resolver library. Red Hat rates this flaw as Important. A remote attacker who can supply DNS responses to an application using a vulnerable c-ares build can send a crafted DNS message containing a long compression-pointer chain that causes quadratic name-decompression work in ares_dns_name_parse(). Because c-ares uses a single-threaded event loop, a single crafted response can stall DNS resolution for the process. Impact is limited to availability; the flaw does not cause memory corruption or information disclosure. The vulnerable DNS name parser is present in c-ares 1.21 and later through 1.34.6 and is fixed in 1.34.7. Red Hat Enterprise Linux 10 ships c-ares 1.25.0 or 1.34.6 and is affected. Red Hat Enterprise Linux 6, 7, 8, and 9 ship older c-ares versions (1.10.x through 1.19.x) that do not include this parser and are not affected. Red Hat\u0027s CVSS v3.1 score is 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H), matching the upstream High rating, because one crafted response is sufficient to deny name resolution.",
          "title": "Statement"
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          "text": "The CVSS score(s) listed for this vulnerability do not reflect the associated product\u0027s status, and are included for informational purposes to better understand the severity of this vulnerability.",
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          "details": "Important"
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      "title": "c-ares: c-ares: CPU exhaustion denial of service via unbounded DNS name compression pointer chains"
    },
    {
      "cve": "CVE-2026-69186",
      "cwe": {
        "id": "CWE-1284",
        "name": "Improper Validation of Specified Quantity in Input"
      },
      "discovery_date": "2026-09-22T17:25:55.228819+00:00",
      "ids": [
        {
          "system_name": "Red Hat Bugzilla ID",
          "text": "2538212"
        }
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      "notes": [
        {
          "category": "description",
          "text": "A flaw was found in c-ares, an asynchronous resolver library. A remote attacker can send a specially crafted DNS response that causes the `ares_dns_parse()` function to trust attacker-controlled record counts without validating if the response contains enough bytes for the claimed records. This can lead to disproportionate heap memory reservation, resulting in a memory-amplification denial of service (DoS) by degrading or denying name resolution.",
          "title": "Vulnerability description"
        },
        {
          "category": "summary",
          "text": "c-ares: c-ares: Denial of Service via unvalidated DNS header record counts",
          "title": "Vulnerability summary"
        },
        {
          "category": "other",
          "text": "A flaw was found in the c-ares asynchronous DNS resolver library. Red Hat rates this flaw as Important. A remote attacker who can supply DNS responses to an application using a vulnerable c-ares build can send a crafted DNS message in which attacker-controlled ANCOUNT, NSCOUNT, and ARCOUNT header fields are trusted by ares_dns_parse() before the library verifies that the response contains enough bytes for the claimed records. Because parsing runs before transaction ID and question validation, a very small message can trigger pre-allocation of disproportionately large resource-record arrays on the heap, and repeated malicious responses can drive large allocation and release cycles that degrade or deny name resolution. Impact is limited to availability; the flaw does not cause memory corruption or information disclosure. The vulnerable pre-allocation path was introduced with the modern DNS record parser (c-ares 1.21 and later) and is fixed in 1.34.7. Red Hat Enterprise Linux 10 ships c-ares 1.25.0 or 1.34.6 and is affected. Red Hat Enterprise Linux 6, 7, 8, and 9 ship older c-ares versions that do not include this parser and are not affected. Red Hat\u0027s severity of Important (CVSS 7.5, AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) is higher than the upstream Moderate rating (CVSS 5.3, A:L) because Red Hat assesses the availability impact of sustained malicious DNS responses on name resolution as high.",
          "title": "Statement"
        },
        {
          "category": "general",
          "text": "The CVSS score(s) listed for this vulnerability do not reflect the associated product\u0027s status, and are included for informational purposes to better understand the severity of this vulnerability.",
          "title": "CVSS score applicability"
        }
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          "category": "self",
          "summary": "Canonical URL",
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          "category": "external",
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          "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-69186"
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          "category": "external",
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          "category": "external",
          "summary": "https://github.com/c-ares/c-ares/releases/tag/v1.34.7",
          "url": "https://github.com/c-ares/c-ares/releases/tag/v1.34.7"
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            "AppStream-10.3.Z:c-ares-debugsource-0:1.34.6-5.el10_3.2.x86_64",
            "AppStream-10.3.Z:c-ares-devel-0:1.34.6-5.el10_3.2.aarch64",
            "AppStream-10.3.Z:c-ares-devel-0:1.34.6-5.el10_3.2.ppc64le",
            "AppStream-10.3.Z:c-ares-devel-0:1.34.6-5.el10_3.2.s390x",
            "AppStream-10.3.Z:c-ares-devel-0:1.34.6-5.el10_3.2.x86_64",
            "BaseOS-10.3.Z:c-ares-0:1.34.6-5.el10_3.2.aarch64",
            "BaseOS-10.3.Z:c-ares-0:1.34.6-5.el10_3.2.ppc64le",
            "BaseOS-10.3.Z:c-ares-0:1.34.6-5.el10_3.2.s390x",
            "BaseOS-10.3.Z:c-ares-0:1.34.6-5.el10_3.2.src",
            "BaseOS-10.3.Z:c-ares-0:1.34.6-5.el10_3.2.x86_64",
            "BaseOS-10.3.Z:c-ares-debuginfo-0:1.34.6-5.el10_3.2.aarch64",
            "BaseOS-10.3.Z:c-ares-debuginfo-0:1.34.6-5.el10_3.2.ppc64le",
            "BaseOS-10.3.Z:c-ares-debuginfo-0:1.34.6-5.el10_3.2.s390x",
            "BaseOS-10.3.Z:c-ares-debuginfo-0:1.34.6-5.el10_3.2.x86_64",
            "BaseOS-10.3.Z:c-ares-debugsource-0:1.34.6-5.el10_3.2.aarch64",
            "BaseOS-10.3.Z:c-ares-debugsource-0:1.34.6-5.el10_3.2.ppc64le",
            "BaseOS-10.3.Z:c-ares-debugsource-0:1.34.6-5.el10_3.2.s390x",
            "BaseOS-10.3.Z:c-ares-debugsource-0:1.34.6-5.el10_3.2.x86_64"
          ]
        }
      ],
      "threats": [
        {
          "category": "impact",
          "details": "Important"
        }
      ],
      "title": "c-ares: c-ares: Denial of Service via unvalidated DNS header record counts"
    }
  ]
}

CVE-2026-69184 (GCVE-0-2026-69184)

Vulnerability from cvelistv5 – Published: 2026-09-18 17:26 – Updated: 2026-09-21 20:48

Title

c-ares: CPU-exhaustion denial of service via unbounded DNS name compression pointer chains

Summary

c-ares is an asynchronous resolver library. Prior to 1.34.7, ares_dns_name_parse() enforces backward DNS compression pointers but does not bound the total pointer hops or assembled name length. A malicious DNS server can send a response containing a long descending pointer chain and many resource records whose NAME or RDATA fields refer to the chain, causing repeated decompression work that grows quadratically with message size. A single crafted response can stall the single-threaded c-ares event loop and deny DNS resolution, without causing memory corruption or information disclosure. This issue is fixed in version 1.34.7.

Severity

7.5 (High)


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

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-18 20:13 UTC

CWE

CWE-407 - Inefficient Algorithmic Complexity

Assigner

GitHub_M CNA under the mitre root

CNA scorecard C 72/100 over 7868 records in the last 180 days details

References

6 references

URL	Tags
https://github.com/c-ares/c-ares/security/advisor…	x_refsource_CONFIRM
https://github.com/c-ares/c-ares/pull/1164	x_refsource_MISC
https://github.com/c-ares/c-ares/pull/1210	x_refsource_MISC
https://github.com/c-ares/c-ares/commit/5c8341ba6…	x_refsource_MISC
https://github.com/c-ares/c-ares/commit/f1288bbc7…	x_refsource_MISC
https://github.com/c-ares/c-ares/releases/tag/v1.34.7	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
c-ares	c-ares	Affected: < 1.34.7

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-69184",
                "options": [
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                    "Exploitation": "none"
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                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-09-18T20:13:18.897117Z",
                "version": "2.0.3"
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          "dateUpdated": "2026-09-21T20:48:59.663Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
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        "title": "CISA ADP Vulnrichment"
      }
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          "lang": "en",
          "value": "c-ares is an asynchronous resolver library. Prior to 1.34.7, ares_dns_name_parse() enforces backward DNS compression pointers but does not bound the total pointer hops or assembled name length. A malicious DNS server can send a response containing a long descending pointer chain and many resource records whose NAME or RDATA fields refer to the chain, causing repeated decompression work that grows quadratically with message size. A single crafted response can stall the single-threaded c-ares event loop and deny DNS resolution, without causing memory corruption or information disclosure. This issue is fixed in version 1.34.7."
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          "cvssV3_1": {
            "attackComplexity": "LOW",
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            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
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          "name": "https://github.com/c-ares/c-ares/pull/1164",
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          "name": "https://github.com/c-ares/c-ares/commit/5c8341ba6ff3a8e4e4dfd616f8ed0418838b8b7b",
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        },
        {
          "name": "https://github.com/c-ares/c-ares/releases/tag/v1.34.7",
          "tags": [
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          "url": "https://github.com/c-ares/c-ares/releases/tag/v1.34.7"
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        "advisory": "GHSA-pjmc-gx33-gc76",
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    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

CVE-2026-69186 (GCVE-0-2026-69186)

Vulnerability from cvelistv5 – Published: 2026-09-18 17:25 – Updated: 2026-09-18 19:51

Title

c-ares: Memory-amplification denial of service via unvalidated DNS header record counts

Summary

c-ares is an asynchronous resolver library. Prior to 1.34.7, ares_dns_parse() trusts the attacker-controlled ANCOUNT, NSCOUNT, and ARCOUNT fields before confirming that the DNS response contains enough bytes for the claimed records. Because process_answer() invokes parsing before transaction ID and question validation, a malicious DNS response can cause ares_dns_record_rr_prealloc() and ares_array_set_size() to reserve disproportionate heap memory for a tiny message. Repeated responses create large allocation and release cycles that can degrade or deny name resolution, without causing memory corruption or information disclosure. This issue is fixed in version 1.34.7.

Severity

5.3 (Medium)


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

SSVC

Exploitation: poc Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-18 19:50 UTC

CWE

CWE-400 - Uncontrolled Resource Consumption

Assigner

GitHub_M CNA under the mitre root

CNA scorecard C 72/100 over 7868 records in the last 180 days details

References

5 references

URL	Tags
https://github.com/c-ares/c-ares/security/advisor…	x_refsource_CONFIRM
https://github.com/c-ares/c-ares/pull/1134	x_refsource_MISC
https://github.com/c-ares/c-ares/commit/e47c203f9…	x_refsource_MISC
https://github.com/c-ares/c-ares/commit/eaded4cb2…	x_refsource_MISC
https://github.com/c-ares/c-ares/releases/tag/v1.34.7	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
c-ares	c-ares	Affected: < 1.34.7

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-69186",
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                  },
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                "timestamp": "2026-09-18T19:50:58.245833Z",
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Sightings

Author	Source	Type	Date	Other

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.

Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

Order JSON

How durations are calculated

Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.

Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.

Publication & reservation Sightings KEV catalogs Other timestamps

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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted

RHSA-2026:98629

CVE-2026-69184 (GCVE-0-2026-69184)

CVE-2026-69186 (GCVE-0-2026-69186)

Tags

Sightings

Nomenclature

Vulnerability timeline

Related by attack behaviour