In the Linux kernel's s390/zcrypt module, the function that generates EP11 CPRB payloads incorrectly uses struct overlays without validating ASN.1 encoding or checking payload bounds. This missing validation allows an attacker to craft a payload that can overflow kernel memory, corrupt kernel state, and potentially execute arbitrary code. The weakness represents an instance of improper input validation and out‑of‑bounds memory access.

The flaw affects all Linux installations that incorporate the s390/zcrypt driver, which is part of the standard Linux kernel distribution. No particular kernel release is specified in the advisory, so any build that has not incorporated the upstream patch remains vulnerable.

The CVSS score is not publicly reported and the EPSS score is unavailable, so the intrinsic severity must be inferred from the capability to corrupt kernel memory. The vulnerability is not listed in the CISA KEV catalog, indicating no known public exploitation. Because the flaw requires delivering a malicious EP11 CPRB payload to the zcrypt device, the attack is likely local or requires privileged execution, though explicit exploitation details are not provided. Until an exploit is observed, the risk is considered high for any system running the vulnerable driver and should be mitigated with the official patch.