The advisory covers an integer overflow vulnerability (CVE-2026-56407) in libexpat's doProlog function caused by improper handling of entity value lengths. This flaw can be exploited by a local attacker to execute arbitrary code or access sensitive data. The vulnerability is rated moderate severity with a CVSS base score of 6.9 by Red Hat. The advisory also references other CVEs (CVE-2026-56404, CVE-2026-56131) related to the Red Hat Hardened Images RPMs. The update includes expat packages version 2.8.2-1.1.hum1 for aarch64 and x86_64 architectures. The advisory recommends disabling internal and external XML entity processing and using a Web Application Firewall to limit XML payload sizes. No explicit patch version or fixed version is provided in the advisory content.

Exploitation of the integer overflow in libexpat can lead to arbitrary code execution or information disclosure on affected systems. The attack requires local access and has high complexity, which limits the likelihood of exploitation in typical environments. The vulnerability affects confidentiality, integrity, and availability to some extent, with potential for crashes or memory corruption. The advisory rates the severity as moderate and notes that the immediate impact on typical Red Hat deployments is limited.

Red Hat recommends explicitly disabling all internal and external XML entity processing within the application's XML parser configuration to prevent exploitation. Additionally, deploying a Web Application Firewall (WAF) to strictly limit the maximum size of incoming XML payloads can help prevent triggering the overflow. The advisory does not provide explicit fixed versions or patches; users should monitor Red Hat's official channels for updates and apply the provided RPM updates when available. No immediate action beyond these mitigations is stated as required.