CVE-2026-33630 Use after free in c-ares
A use-after-free in c-ares allows remote attackers to execute code or cause denial of service via TCP queries.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-33630?
CVE-2026-33630 is a high-severity use after free vulnerability in c-ares, published on 3 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
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.
Which versions are affected by CVE-2026-33630?
Linux distribution packages (9)
c-ares AlmaLinux:10 | All versions | 1.34.6-2.el10_2 |
c-ares-devel AlmaLinux:10 | All versions | 1.34.6-2.el10_2 |
c-ares Red Hat:enterprise_linux:10.2 | All versions | 0:1.34.6-2.el10_2 |
c-ares-debuginfo Red Hat:enterprise_linux:10.2 | All versions | 0:1.34.6-2.el10_2 |
c-ares-debugsource Red Hat:enterprise_linux:10.2 | All versions | 0:1.34.6-2.el10_2 |
c-ares-devel Red Hat:enterprise_linux:10.2 | All versions | 0:1.34.6-2.el10_2 |
c-ares Red Hat:hummingbird:1 | All versions | 0:1.34.7-1.hum1 |
c-ares-devel Red Hat:hummingbird:1 | All versions | 0:1.34.7-1.hum1 |
c-ares Rocky Linux:10 | All versions | 0:1.34.6-2.el10_2 |
How do I fix CVE-2026-33630?
Upgrade to a fixed version.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-33630 being exploited?
There is no known exploitation of CVE-2026-33630 in the wild and no public exploit code.
Sources
Also known as ALPINE-CVE-2026-33630, ALSA-2026:42096, AZL-99093, AZL-99095, BELL-CVE-2026-33630, DEBIAN-CVE-2026-33630 and 9 more.