Vulnerability-Lookup

CVE-2026-8674 (GCVE-0-2026-8674)

Vulnerability from cvelistv5 – Published: 2026-09-17 16:54 – Updated: 2026-09-17 18:09

Title

Assertion failure in the DNS stub resolver with a long search domain

Summary

Initializing the DNS stub resolver from an /etc/resolv.conf file, or a LOCALDOMAIN environment variable, whose search list contains a domain of roughly 200 characters or more in the GNU C Library version 2.26 to 2.44 results in an assertion failure which aborts the process. The resolver truncates the search list when copying it into the fixed-size _res.defdname buffer, then asserts that the copy is consistent with the full configuration. The consistency check compared against the wrong size and did not handle a first entry that does not fit, so a correctly truncated list failed the assertion. Any process that resolves names through the library is affected, including long-running processes that reload /etc/resolv.conf on the next query after it changes. Search domains are commonly written to /etc/resolv.conf from data received over DHCP or from a VPN server, so an attacker on the local network may be able to trigger this without privileges on the target system, subject to validation by the network configuration software.

Severity

5.3 (Medium)


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

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-17 18:05 UTC

CWE

CWE-617 - Reachable Assertion

Assigner

glibc redhat root

References

5 references

URL	Tags
https://sourceware.org/bugzilla/show_bug.cgi?id=31026	issue-tracking
https://sourceware.org/git/?p=glibc.git;a=blob_pl…	vendor-advisory
https://sourceware.org/git/?p=glibc.git;a=commit;…	patch
https://joshua.hu/fuzzing-glibc-libresolv	technical-description
http://www.openwall.com/lists/oss-security/2026/09/17/4

Impacted products

1 product

Vendor	Product	Version	CPE status
The GNU C Library	glibc	Affected: 2.26 , ≤ 2.44 (custom)	guessed

Date Public

2023-11-07 05:00

Credits

Joshua Rogers

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-8674

Vulnerability from fkie_nvd - Published: 2026-09-17 17:16 - Updated: 2026-09-17 19:17

Severity

5.3 (Medium) - CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

Summary

References

	URL	Tags
	3ff69d7a-14f2-4f67-a097-88dee7810d18	https://joshua.hu/fuzzing-glibc-libresolv
	3ff69d7a-14f2-4f67-a097-88dee7810d18	https://sourceware.org/bugzilla/show_bug.cgi?id=31026
	3ff69d7a-14f2-4f67-a097-88dee7810d18	https://sourceware.org/git/?p=glibc.git;a=blob_plain;f=advisories/GLIBC-SA-2026-0021
	3ff69d7a-14f2-4f67-a097-88dee7810d18	https://sourceware.org/git/?p=glibc.git;a=commit;h=506ea57086bfb9ce3daff1c14246a1cb532aba0a
	af854a3a-2127-422b-91ae-364da2661108	http://www.openwall.com/lists/oss-security/2026/09/17/4

Impacted products

	Vendor	Product	Version

JSON

To clipboard

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            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-09-17T18:05:54.714741Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-09-17T17:16:53.220",
  "references": [
    {
      "source": "3ff69d7a-14f2-4f67-a097-88dee7810d18",
      "url": "https://joshua.hu/fuzzing-glibc-libresolv"
    },
    {
      "source": "3ff69d7a-14f2-4f67-a097-88dee7810d18",
      "url": "https://sourceware.org/bugzilla/show_bug.cgi?id=31026"
    },
    {
      "source": "3ff69d7a-14f2-4f67-a097-88dee7810d18",
      "url": "https://sourceware.org/git/?p=glibc.git;a=blob_plain;f=advisories/GLIBC-SA-2026-0021"
    },
    {
      "source": "3ff69d7a-14f2-4f67-a097-88dee7810d18",
      "url": "https://sourceware.org/git/?p=glibc.git;a=commit;h=506ea57086bfb9ce3daff1c14246a1cb532aba0a"
    },
    {
      "source": "af854a3a-2127-422b-91ae-364da2661108",
      "url": "http://www.openwall.com/lists/oss-security/2026/09/17/4"
    }
  ],
  "sourceIdentifier": "3ff69d7a-14f2-4f67-a097-88dee7810d18",
  "vulnStatus": "Received",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-617"
        }
      ],
      "source": "3ff69d7a-14f2-4f67-a097-88dee7810d18",
      "type": "Secondary"
    }
  ]
}

GHSA-QGHR-QHFC-4HXP

Vulnerability from github – Published: 2026-09-17 18:31 – Updated: 2026-09-17 21:31

Details

The resolver truncates the search list when copying it into the fixed-size _res.defdname buffer, then asserts that the copy is consistent with the full configuration. The consistency check compared against the wrong size and did not handle a first entry that does not fit, so a correctly truncated list failed the assertion. Any process that resolves names through the library is affected, including long-running processes that reload /etc/resolv.conf on the next query after it changes. Search domains are commonly written to /etc/resolv.conf from data received over DHCP or from a VPN server, so an attacker on the local network may be able to trigger this without privileges on the target system, subject to validation by the network configuration software.

Severity

5.3 (Medium)


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

Show details on source website

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{
  "affected": [],
  "aliases": [
    "CVE-2026-8674"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-617"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-09-17T17:16:53Z",
    "severity": "MODERATE"
  },
  "details": "Initializing the DNS stub resolver from an /etc/resolv.conf file, or a LOCALDOMAIN environment variable, whose search list contains a domain of roughly 200 characters or more in the GNU C Library version 2.26 to 2.44 results in an assertion failure which aborts the process.\n\nThe resolver truncates the search list when copying it into the fixed-size _res.defdname buffer, then asserts that the copy is consistent with the full configuration.  The consistency check compared against the wrong size and did not handle a first entry that does not fit, so a correctly truncated list failed the assertion.  Any process that resolves names through the library is affected, including long-running processes that reload /etc/resolv.conf on the next query after it changes.  Search domains are commonly written to /etc/resolv.conf from data received over DHCP or from a VPN server, so an attacker on the local network may be able to trigger this without privileges on the target system, subject to validation by the network configuration software.",
  "id": "GHSA-qghr-qhfc-4hxp",
  "modified": "2026-09-17T21:31:41Z",
  "published": "2026-09-17T18:31:48Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-8674"
    },
    {
      "type": "WEB",
      "url": "https://joshua.hu/fuzzing-glibc-libresolv"
    },
    {
      "type": "WEB",
      "url": "https://sourceware.org/bugzilla/show_bug.cgi?id=31026"
    },
    {
      "type": "WEB",
      "url": "https://sourceware.org/git/?p=glibc.git;a=blob_plain;f=advisories/GLIBC-SA-2026-0021"
    },
    {
      "type": "WEB",
      "url": "https://sourceware.org/git/?p=glibc.git;a=commit;h=506ea57086bfb9ce3daff1c14246a1cb532aba0a"
    },
    {
      "type": "WEB",
      "url": "http://www.openwall.com/lists/oss-security/2026/09/17/4"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}

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.

Detection rules are retrieved from Rulezet.

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

CVE-2026-8674 (GCVE-0-2026-8674)

FKIE_CVE-2026-8674

GHSA-QGHR-QHFC-4HXP

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