CVE-2025-31498

Description

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.

How to fix CVE-2025-31498

To remediate CVE-2025-31498, upgrade the affected package to a fixed version below.

• —upgrade to 1.34.5-r0 or later
• —upgrade to 1.34.5-1 or later

Is CVE-2025-31498 being exploited?

Low — EPSS is 0.7%, meaning exploitation activity has not been observed at scale.

Affected packages (2)

• from 0, < 1.34.5-r0
• from 0, < 1.34.5-1

CVSS scores

References (2)

• ADVISORYsecurity.alpinelinux.org/vuln/CVE-2025-31498
• ADVISORYsecurity-tracker.debian.org/tracker/CVE-2025-31498