CVE-2025-31498: c-ares has a use-after-free in read_answers()
First published: Tue Apr 08 2025(Updated: )
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.
Credit: security-advisories@github.com
| Affected Software | Affected Version | How to fix |
|---|---|---|
| c-ares | >=1.32.3<1.34.4 |
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Reference Links
Frequently Asked Questions
What is the severity of CVE-2025-31498?
The severity of CVE-2025-31498 is classified as a high-severity vulnerability due to the potential for remote code execution.
How do I fix CVE-2025-31498?
To fix CVE-2025-31498, upgrade c-ares to version 1.34.5 or later, which addresses the use-after-free vulnerability.
What causes the CVE-2025-31498 vulnerability?
CVE-2025-31498 is caused by a use-after-free condition in the read_answers() function related to re-enqueuing queries under specific conditions.
Which versions of c-ares are affected by CVE-2025-31498?
CVE-2025-31498 affects c-ares versions from 1.32.3 to 1.34.4.
Is CVE-2025-31498 related to DNS queries?
Yes, CVE-2025-31498 is related to DNS queries and occurs when the upstream server does not properly support EDNS or due to DNS Cookie failures.
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