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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-69184
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-18 18:17:11 UTC
Updated2026-09-18 18:17:11 UTC
Descriptionc-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.

Risk And Classification

Primary CVSS: v3.1 7.5 HIGH from [email protected]

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

EPSS: 0.006750000 probability, percentile 0.507560000 (date 2026-09-20)

Problem Types: CWE-407 | CWE-407 CWE-407: Inefficient Algorithmic Complexity

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.1CNADECLARED7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA C-ares C-ares affected < 1.34.7 Not specified

References

ReferenceSourceLinkTags
github.com/c-ares/c-ares/pull/1210 [email protected] github.com
github.com/c-ares/c-ares/commit/5c8341ba6ff3a8e4e4dfd616f8ed0418838b8b7b [email protected] github.com
github.com/c-ares/c-ares/releases/tag/v1.34.7 [email protected] github.com
github.com/c-ares/c-ares/commit/f1288bbc70e9a1e0a77134c2382157e52d326aea [email protected] github.com
github.com/c-ares/c-ares/pull/1164 [email protected] github.com
github.com/c-ares/c-ares/security/advisories/GHSA-pjmc-gx33-gc76 [email protected] github.com
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