Double free in c-ares - #VU162898
Published: November 9, 2026
Vulnerability identifier: #VU162898
CSH Severity: Medium
CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: N/A
CWE-ID: CWE-415
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows an unauthenticated remote attacker to crash an affected application using c-ares, causing denial of service.
The vulnerability exists due to a double free when c-ares invokes a query callback before completing lookup removal after connection failure, in applications that call ares_cancel() from that callback. An unauthenticated remote attacker can close or refuse lookup connections until retries are exhausted, triggering the callback and a second release of the lookup.
Affected software
c-ares
Remediation
Install security update from vendor's website.
c-ares - update to 1.34.9