CVE-2026-69184 c-ares: CPU-exhaustion denial of service via unbounded DNS name compression pointer chains
A malicious DNS server can cause CPU exhaustion and deny DNS resolution in c-ares by sending crafted responses with unbounded compression pointer chains.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-69184?
CVE-2026-69184 is a high-severity denial of service vulnerability in c-ares, published on 18 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. 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.
Weakness: CWE-407
Which versions are affected by CVE-2026-69184?
How do I fix CVE-2026-69184?
Upgrade to a fixed version.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-69184 being exploited?
There is no known exploitation of CVE-2026-69184 in the wild and no public exploit code.
Sources
Also known as AZL-103307, AZL-103457, BELL-CVE-2026-69184, DEBIAN-CVE-2026-69184, ECHO-f279-6f91-2224, GHSA-pjmc-gx33-gc76 and 3 more.