CVE-2026-69184
c-ares: CPU-exhaustion denial of service via unbounded DNS name compression pointer chains
- State
- Published
- Severity
- 7.5 High
- Published
- Sep 18, 2026
- Updated
- Sep 21, 2026
- Reserved
- Aug 3, 2026
Description
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 3.1 | 7.5 High | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | GitHub_M |
Weaknesses
- CWE-407 Inefficient Algorithmic Complexity
Affected Products
| Product | Versions |
|---|---|
c-aresc-ares |
|
References
- https://github.com/c-ares/c-ares/security/advisories/GHSA-pjmc-gx33-gc76
- https://github.com/c-ares/c-ares/pull/1164
- https://github.com/c-ares/c-ares/pull/1210
- https://github.com/c-ares/c-ares/commit/5c8341ba6ff3a8e4e4dfd616f8ed0418838b8b7b
- https://github.com/c-ares/c-ares/commit/f1288bbc70e9a1e0a77134c2382157e52d326aea
- https://github.com/c-ares/c-ares/releases/tag/v1.34.7
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