CVE-2026-64559: 
Linux Kernel Schwachstellenanalyse und -minderung

CVE-2026-64559 is a buffer access vulnerability in the Linux kernel's s390/pkey subsystem, specifically in the PKEY_VERIFYPROTK ioctl handler, which fails to validate the buffer length parameter supplied by user-space. This allows a local attacker with low privileges to trigger an out-of-bounds buffer access, potentially causing a kernel crash or memory corruption. The vulnerability was published on July 29, 2026, and affects Linux kernel versions starting from commit 8fcc231ce3bea12b78bb94b280cdc03cff342435 through multiple stable branches. It carries a CVSS v3.1 base score of 7.8 (High) (GitHub Advisory, Red Hat Bugzilla).

The root cause is classified as CWE-805 (Buffer Access with Incorrect Length Value): the PKEY_VERIFYPROTK ioctl handler in the s390/pkey subsystem processes a user-supplied buffer length without first verifying that it does not exceed the actual allocated buffer size. An attacker with local access can craft an ioctl request specifying an oversized length value, causing the kernel to access memory beyond the intended buffer boundary. Exploitation requires only low privileges (e.g., a standard user account with access to the pkey ioctl interface) and no user interaction. No public proof-of-concept code has been identified at this time (GitHub Advisory, Red Hat Bugzilla).

Successful exploitation can result in a kernel crash (denial of service) or kernel memory corruption, which may further enable privilege escalation or information disclosure on affected IBM s390/z-series systems running vulnerable Linux kernel versions. The confidentiality, integrity, and availability impacts are all rated High, reflecting the potential for an attacker to read sensitive kernel memory, corrupt kernel data structures, or crash the system entirely. The scope is limited to the local system, but kernel-level memory corruption could facilitate further lateral movement within a multi-tenant or containerized environment (GitHub Advisory).

Patches have been released for the affected stable kernel branches: version 6.12.97 (for the 6.12.x series), 6.18.40 (for the 6.18.x series), 7.1.5 (for the 7.1.x series), and 7.2-rc1 for the mainline. Administrators should update to one of these patched versions as soon as possible. As a temporary workaround where immediate patching is not feasible, restrict user access to the pkey ioctl interface through system access controls and user privilege restrictions (GitHub Advisory, Red Hat Bugzilla).