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
An algorithm in a product has an inefficient worst-case computational complexity that may be detrimental to system performance and can be triggered by an attacker, typically using crafted manipulations that ensure that the worst case is being reached.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| C-ares | Ubuntu | upstream | * |
References
- https://github.com/c-ares/c-ares/commit/5c8341ba6ff3a8e4e4dfd616f8ed0418838b8b7b
- https://github.com/c-ares/c-ares/commit/f1288bbc70e9a1e0a77134c2382157e52d326aea
- https://github.com/c-ares/c-ares/pull/1164
- https://github.com/c-ares/c-ares/pull/1210
- https://github.com/c-ares/c-ares/releases/tag/v1.34.7
- https://github.com/c-ares/c-ares/security/advisories/GHSA-pjmc-gx33-gc76