DEBIAN-CVE-2025-31498
Record from OSV · Published April 8, 2025
c-ares is an asynchronous resolver library. From 1.32.3 through 1.34.4, there is a use-after-free in read_answers() when process_answer() may re-enqueue a query either due to a DNS Cookie Failure or when the upstream server does not properly support EDNS, or possibly on TCP queries if the remote closed the connection immediately after a response. If there was an issue trying to put that new transaction on the wire, it would close the connection handle, but read_answers() was still expecting the connection handle to be available to possibly dequeue other responses. In theory a remote attacker might be able to trigger this by flooding the target with ICMP UNREACHABLE packets if they also control the upstream nameserver and can return a result with one of those conditions, this has been untested. Otherwise only a local attacker might be able to change system behavior to make send()/write() return a failure condition. This vulnerability is fixed in 1.34.5.
Fixed versions
Upgrade to a fixed version or later. Language registries are listed first, then Linux distributions, then vendor products.
| Package | Ecosystem | Fixed in |
|---|---|---|
| c-ares | Debian:14 | 1.34.5-1 |
| c-ares | Debian:13 | 1.34.5-1 |
Risk scores
Affected products
| Vendor | Product | Versions |
|---|---|---|
| Debian:14 | c-ares | 0 |
| Debian:13 | c-ares | 0 |
Timeline
- Apr 8, 2025 CVE Published
- Sep 1, 2026 CVE Updated
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