The libexpat XML parsing library versions prior to 2.8.4 do not track handler call depth properly when custom encoding callbacks are used. This flaw can lead to a use-after-free condition, where memory is accessed after it has been freed, potentially causing undefined behavior or crashes. The vulnerability is categorized under CWE-416 (Use After Free) and has a CVSS 3.1 base score of 4.9, indicating a medium severity level. No official patch or remediation information is provided in the available data, and no known exploits are reported in the wild. This issue is similar to other use-after-free vulnerabilities in libexpat identified as CVE-2026-50219, CVE-2026-56131, and CVE-2026-56412.

Successful exploitation could lead to memory corruption resulting in limited confidentiality, integrity, and availability impacts. The CVSS vector indicates that the attack requires local access with high attack complexity and no privileges or user interaction, limiting the ease of exploitation. The impact includes potential information disclosure, data modification, or application crashes.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Since no official fix or patch information is provided, users should monitor libexpat project advisories for updates addressing this vulnerability. Until a patch is available, avoid using custom encoding callbacks if possible or apply other vendor-recommended mitigations once published.