A heap overflow flaw exists in the X.Org Server and its XWayland component where the size of key symbol data calculated in XkbSizeKeySyms() does not match the buffer length used in XkbWriteKeySyms(), allowing an attacker to supply oversized input and overwrite heap memory. This mismatch can corrupt program state and, if the attacker controls the overwritten data, may enable arbitrary code execution or crash the X server to achieve denial‑of‑service.

Red Hat Enterprise Linux distributions from RHEL 6 through RHEL 10, including all extended lifecycle and update support branches, provide the vulnerable X.Org and XWayland packages. Any RHEL system running these components without a patched version is exposed.

The CVSS base score of 7.8 indicates high severity. The EPSS score of <1% implies a low current exploitation likelihood, and the defect is not listed in CISA KEV. Nevertheless, because the flaw can lead to remote code execution, the risk remains significant. No documented exploit is publicly available, so the attack vector is inferred to be a local or remote attacker able to interact with the X server or XWayland, for example through malicious client applications or network connections. Monitoring for suspicious activity and applying the patch are strongly recommended.