Use-after-free in c-ares - #VU156263
Published: October 20, 2026
Vulnerability identifier: #VU156263
CSH Severity: Medium
CVSS v4: 8.2 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: N/A
CWE-ID: CWE-416
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to cause a denial of service by crashing an application using c-ares.
The vulnerability exists due to use-after-free in c-ares lookup handling when an application cancels lookups or reconfigures servers from within a server-state callback registered through ares_set_server_state_callback(). A remote attacker can trigger a lookup timeout or an error reply such as SERVFAIL to invoke the callback, causing c-ares to continue accessing freed lookup or server memory and crash the process.
Affected software
c-ares
Remediation
Install security update from vendor's website.
c-ares - update to 1.34.9