CVE-2026-56407 describes an integer overflow or wraparound issue in the libexpat XML parsing library before version 2.8.2. The vulnerability occurs in the doProlog function, specifically involving the storeEntityValue and the entity textLen parameter. This flaw can cause memory corruption or unexpected behavior due to integer overflow, potentially leading to confidentiality and integrity compromises. The CVSS 3.1 base score is 6.9, with attack vector local, high attack complexity, no privileges required, no user interaction, unchanged scope, and high impact on confidentiality and integrity, and low impact on availability. There is no vendor advisory or patch information currently available to confirm remediation status.

Successful exploitation of this integer overflow could allow an attacker with local access to compromise confidentiality and integrity of the affected system. The availability impact is low. No known exploits are reported in the wild at this time.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is released, avoid processing untrusted XML data with affected versions of libexpat or apply other protective measures such as input validation or sandboxing where feasible.