CVE-2026-56403 is an integer overflow vulnerability in the libexpat XML parsing library affecting versions before 2.8.2. The overflow occurs in the storeAtts function, potentially allowing an attacker to cause memory corruption or other unintended behavior. The CVSS 3.1 base score is 6.9, reflecting medium severity with local attack vector, high attack complexity, no privileges required, no user interaction, unchanged scope, and high impact on confidentiality and integrity with low impact on availability. No vendor advisory or patch information is currently available to confirm remediation status.

The integer overflow may allow an attacker with local access to cause memory corruption, potentially leading to unauthorized disclosure or modification of data (high confidentiality and integrity impact) and limited disruption of service (low availability impact). Exploitation requires local access and has high complexity, reducing the likelihood of widespread exploitation. No known exploits are reported in the wild.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, avoid using vulnerable versions of libexpat or restrict local access to systems using affected versions to mitigate risk.