Use-after-free in c-ares - #VU156257
Published: October 20, 2026
Vulnerability identifier: #VU156257
CSH Severity: Low
CVSS v4: 6.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: N/A
CWE-ID: CWE-416
Exploitation vector: Local access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a local user to cause a denial of service by crashing an application using c-ares.
The vulnerability exists due to use-after-free in c-ares connection handling when a socket-state callback cancels lookups or reconfigures servers while a connection is being opened. A local user can trigger an ordinary lookup in an application with this callback behavior to cause the connection to be released before c-ares finishes using it, resulting in a process crash.
Affected software
c-ares
Remediation
Install security update from vendor's website.
c-ares - update to 1.34.9