CVE-2026-56132 is a heap-based buffer overflow vulnerability in the libexpat XML parsing library prior to version 2.8.2. The issue arises in the doProlog function within xmlparse.c, where improper handling of scaffold backing array reallocation occurs when data structures are shared across multiple parsers. This incorrect synchronization leads to memory corruption, potentially allowing an attacker with local access and high attack complexity to cause a crash or execute arbitrary code. The vulnerability has no known exploits in the wild and no official patch or remediation level has been published yet.

Successful exploitation of this vulnerability could result in a heap-based buffer overflow, leading to potential arbitrary code execution or denial of service. The CVSS score reflects high confidentiality and integrity impact, with a low availability impact. However, exploitation requires local access and high attack complexity, with no privileges or user interaction needed.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is released, avoid sharing data structures across parsers in libexpat or restrict usage to trusted inputs. Monitor vendor communications for updates on patches or official mitigations.