Vulnerability · Published Sep 3, 2026 · Assigned by GitHub_M
CVE-2026-33630c-ares : Use-after-free / double-free in c-ares query-completion handling, remotely triggerable via ares_getaddrinfo() over TCP
High 7.5
In plain English
A high-severity double free 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 0.8% (higher than 58% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
c-ares is an asynchronous resolver library. From ver 1.32.3 until 1.34.7, a use-after-free / double-free in c-ares' query-completion handling. The same flaw — a query's callback being invoked while the query is still linked in the channel's internal lookup structures — is present at multiple points in the resend/finish path (timeout handling, response handling, and query dispatch). If the query, or for ares_getaddrinfo() the owning host_query, is freed as a side effect of that callback, it is then accessed and/or freed a second time. This vulnerability is fixed in ver 1.34.7.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux:10 | c-ares | 1.34.6-2.el10_2 | ALSA-2026:42096 |
| AlmaLinux:10 | c-ares-devel | 1.34.6-2.el10_2 | ALSA-2026:42096 |
| Alpine:v3.21 | c-ares | 1.34.8-r0 | ALPINE-CVE-2026-33630 |
| Alpine:v3.22 | c-ares | 1.34.8-r0 | ALPINE-CVE-2026-33630 |
| Alpine:v3.23 | c-ares | 1.34.8-r0 | ALPINE-CVE-2026-33630 |
| Alpine:v3.24 | c-ares | 1.34.8-r0 | ALPINE-CVE-2026-33630 |
| Debian:13 | c-ares | no fix listed | DEBIAN-CVE-2026-33630 |
| Debian:14 | c-ares | 1.34.7-1 | DEBIAN-CVE-2026-33630 |
| Rocky Linux:10 | c-ares | 0:1.34.6-2.el10_2 | RLSA-2026:42096 |
| Ubuntu:25.10 | c-ares | no fix listed | UBUNTU-CVE-2026-33630 |
| Ubuntu:26.04:LTS | c-ares | 1.34.6-1ubuntu0.1 | USN-8844-1 |
| Ubuntu:26.04:LTS | c-ares | 1.34.6-1ubuntu0.1 | UBUNTU-CVE-2026-33630 |
Affected products (as reported)
Weakness: CWE-415, CWE-416 · 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-6wfj-rwm7-3542 x_refsource_CONFIRM
- https://github.com/c-ares/c-ares/pull/1237 x_refsource_MISC
- https://github.com/c-ares/c-ares/commit/1fa3b86a0b8d18fe7b60f3228a01d770feb026bc x_refsource_MISC
- https://github.com/c-ares/c-ares/commit/d823199b688052dcdc1646f2ab4cb8c16b1c644a x_refsource_MISC
- https://github.com/c-ares/c-ares/releases/tag/v1.34.7 x_refsource_MISC