AIKIDO-2026-534453
c-ares.c-ares is vulnerable to Denial of Service (DoS)
75
High Risk
This Affects:
c-ares.c-aresTL;DR
Name decompression in c-ares follows DNS compression pointers with no cap on the number of hops or the assembled name length. A response that builds a long pointer chain and points many records at that chain repeats the walk for every record. Because resolution runs on one event loop thread, one response can stall every lookup in the process. The fix caps compression hops at 128 and enforces the 255 octet limit while the name is assembled.
Who does this affect?
You are affected if you are using a version that falls within the vulnerable range.
Background info
c-ares.c-ares is vulnerable to Denial of Service (DoS) in versions 1.22.0 - 1.34.6.
How to fix this
Upgrade the c-ares.c-ares and/or the c-ares library to the patch version.
Links
GitHub Release
Fix Commits
github.com/c-ares/c-ares/commit/5c8341ba6ff3a8e4e4dfd616f8ed0418838b8b7bgithub.com/c-ares/c-ares/commit/f1288bbc70e9a1e0a77134c2382157e52d326aea
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