Vulnerability · Published Sep 18, 2026 · Assigned by GitHub_M
CVE-2026-69184c-ares: CPU-exhaustion denial of service via unbounded DNS name compression pointer chains
High 7.5
In plain English
A high-severity security flaw in c-ares from c-ares. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 42% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:13 | c-ares | no fix listed | DEBIAN-CVE-2026-69184 |
| Debian:14 | c-ares | 1.34.7-1 | DEBIAN-CVE-2026-69184 |
| Ubuntu:22.04:LTS | c-ares | 1.18.1-1ubuntu0.22.04.4 | UBUNTU-CVE-2026-69184 |
| Ubuntu:22.04:LTS | c-ares | 1.18.1-1ubuntu0.22.04.4 | USN-8951-1 |
| Ubuntu:24.04:LTS | c-ares | 1.27.0-1.0ubuntu1.1 | USN-8951-1 |
| Ubuntu:24.04:LTS | c-ares | 1.27.0-1.0ubuntu1.1 | UBUNTU-CVE-2026-69184 |
| Ubuntu:26.04:LTS | c-ares | 1.34.6-1ubuntu0.2 | USN-8951-1 |
| Ubuntu:26.04:LTS | c-ares | 1.34.6-1ubuntu0.2 | UBUNTU-CVE-2026-69184 |
Affected products (as reported)
Weakness: CWE-407 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
References
- https://github.com/c-ares/c-ares/security/advisories/GHSA-pjmc-gx33-gc76 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/5c8341ba6ff3a8e4e4dfd616f8ed0418838b8b7b x_refsource_MISC
- https://github.com/c-ares/c-ares/commit/f1288bbc70e9a1e0a77134c2382157e52d326aea x_refsource_MISC
- https://github.com/c-ares/c-ares/releases/tag/v1.34.7 x_refsource_MISC