CVE-2026-0989 identifies a vulnerability in the RelaxNG parser component of libxml2, a widely used XML parsing library included in Red Hat Enterprise Linux 10. The issue stems from the parser's handling of external schema inclusions via nested <include> directives. Specifically, the parser does not enforce a maximum recursion depth when resolving these nested includes, allowing specially crafted or excessively complex schemas to induce uncontrolled recursion. This uncontrolled recursion can exhaust the stack space, causing the parsing application to crash. The consequence is a denial-of-service (DoS) condition, where legitimate services relying on XML schema validation may become unavailable. The vulnerability is remotely exploitable without authentication or user interaction but requires a high level of attack complexity due to the need to craft complex schemas. The CVSS v3.1 score is 3.7 (low), reflecting the limited impact confined to availability with no confidentiality or integrity compromise. No known exploits have been reported in the wild, and no patches have been explicitly linked yet, though Red Hat is the vendor responsible for addressing the issue. This vulnerability primarily affects applications and services that utilize libxml2’s RelaxNG parser for XML schema validation, which may include configuration management, data interchange, or security policy enforcement components within Red Hat Enterprise Linux 10 environments.

For European organizations, the primary impact is a potential denial-of-service condition affecting applications that parse XML schemas using libxml2’s RelaxNG parser on Red Hat Enterprise Linux 10. This could disrupt critical services that rely on XML validation, such as configuration management tools, network devices, or security policy enforcement systems. Although the vulnerability does not compromise data confidentiality or integrity, service availability interruptions could lead to operational downtime, affecting business continuity and potentially causing financial or reputational damage. Organizations in sectors with high reliance on Red Hat Enterprise Linux 10, such as finance, telecommunications, government, and critical infrastructure, may experience service degradation or outages if targeted. The lack of known exploits and the high complexity of attack reduce immediate risk, but the vulnerability remains a concern for environments where XML schema processing is integral to service delivery.

European organizations should implement the following specific mitigations: 1) Monitor Red Hat security advisories closely for patches addressing CVE-2026-0989 and apply updates promptly once available. 2) Restrict the acceptance of external XML schemas from untrusted or unauthenticated sources to prevent malicious schema injection. 3) Implement resource limits (e.g., stack size, CPU time) on processes performing XML schema parsing to mitigate the impact of excessive recursion. 4) Where feasible, replace or supplement RelaxNG schema validation with alternative methods that enforce recursion limits or use safer parsing libraries. 5) Conduct code reviews and testing of applications that utilize libxml2’s RelaxNG parser to identify and remediate potential abuse vectors. 6) Employ runtime monitoring and anomaly detection to identify unusual application crashes or resource exhaustion patterns indicative of exploitation attempts. These targeted actions go beyond generic advice by focusing on controlling schema inputs, enforcing resource constraints, and proactive patch management.