{"id":"AZL-59742","summary":"CVE-2025-31498 affecting package fluent-bit for versions less than 3.1.9-4","details":"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.","modified":"2026-04-01T05:19:52.051491Z","published":"2025-04-08T14:15:35Z","upstream":["CVE-2025-31498"],"references":[{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-31498"}],"affected":[{"package":{"name":"fluent-bit","ecosystem":"Azure Linux:3","purl":"pkg:rpm/azure-linux/fluent-bit"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.1.9-4"}]}],"database_specific":{"source":"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-59742.json"}}],"schema_version":"1.7.5"}