CVE-2025-26597 is a buffer overflow vulnerability identified in the X.Org and Xwayland components, specifically within the function XkbChangeTypesOfKey(). This function manages keyboard key types and their associated groups and actions. When called with a group parameter of zero, the function resizes the key symbols table to zero but does not adjust the key actions array accordingly, leaving it at its previous size. If the function is later invoked with a non-zero group value, the mismatch between the resized key symbols table and the unchanged key actions array leads to a buffer overflow condition. This memory corruption flaw can be exploited to overwrite adjacent memory, potentially allowing an attacker to execute arbitrary code or cause a denial of service. The vulnerability requires local access with low privileges (AV:L, PR:L) and does not require user interaction (UI:N). The scope is unchanged (S:U), but the impact on confidentiality, integrity, and availability is high (C:H/I:H/A:H), as indicated by the CVSS 3.1 base score of 7.8. No public exploits are currently known, but the flaw affects versions from 0 up to 22.0.0, which covers a broad range of deployments. The vulnerability was reserved and published in February 2025, with enrichment from CISA and Red Hat assigners. The flaw is critical for systems relying on X.Org or Xwayland for graphical input handling, especially in Linux environments.

For European organizations, this vulnerability poses a significant risk due to the widespread use of Linux-based systems with X.Org and Xwayland in enterprise, academic, and government environments. Successful exploitation could allow an attacker with local access to escalate privileges, execute arbitrary code, or cause system crashes, impacting confidentiality, integrity, and availability of critical systems. This is particularly concerning for sectors such as finance, telecommunications, energy, and public administration, where Linux graphical environments are common. The vulnerability could be leveraged to compromise user sessions, steal sensitive information, or disrupt services. Given the requirement for local access, insider threats or compromised user accounts represent the primary attack vectors. The absence of known exploits currently provides a window for proactive mitigation, but the high severity score demands urgent patching and monitoring to prevent potential exploitation.

1. Apply security patches from X.Org and Xwayland maintainers immediately once available to address the buffer overflow flaw. 2. Restrict local access to systems running vulnerable versions by enforcing strict user account controls and limiting administrative privileges. 3. Monitor system logs and behavior for anomalies related to keyboard input handling or unexpected crashes in X.Org/Xwayland processes. 4. Employ application whitelisting and runtime protection tools to detect and prevent exploitation attempts targeting this vulnerability. 5. Conduct regular audits of user access and session activity to identify potential insider threats or compromised accounts. 6. Where possible, consider migrating to Wayland-only environments or alternative display servers that do not use the vulnerable code paths. 7. Educate system administrators and users about the risks of local privilege escalation vulnerabilities and the importance of maintaining updated software stacks.