GNU C Library CVE-2026-97399

Exploitation is limited to systems running glibc 2.24 or later on the IBM POWER8 architecture, where the Power8-optimized strncasecmp implementation is used. It further requires that both compared strings be attacker-controlled and match all the way to the last byte of a memory page whose neighbouring page is unmapped or non-readable - only then does the one-byte over-read fault. These conditions (specific CPU family plus precise page-boundary alignment) make triggering non-deterministic and account for the AC:H rating; impact is limited to crashing the affected process (A:L), with no code execution, data disclosure, or data modification.

This is a low-severity availability-only issue, and all signals agree it is not a priority. The provided CVSS 3.1 vector (AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L, base 3.7) reflects a one-byte out-of-bounds read (CWE-126) in the Power8-optimized strncasecmp that can only crash the calling program - no confidentiality or integrity impact, and A:L rather than A:H because a single unreadable byte causes at most a segfault of one process, not sustained service denial. Attack complexity is High, correctly, because the read only faults under a narrow memory layout: the attacker-controlled strings must match up to the exact edge of a mapped page whose neighbour is unmapped or unreadable. No EPSS score, KEV listing, or POC was provided in the input, so there is no public exploit identified at time of analysis and no evidence of active exploitation. The network attack vector (AV:N) is justified only in the sense that the triggering strings can be attacker-supplied through an application that forwards remote input into strncasecmp; the fault itself is a local memory read within the process. Net: genuine but very low real-world risk - a reliability bug on one CPU family, not a security emergency.

An attacker supplies two strings to an application running on POWER8 hardware (e.g. via a network field the app compares with strncasecmp) that are identical up to the final byte of a memory page, where the adjacent page is unmapped. The optimized comparison reads one byte past the limit, faults, and crashes the process, causing a denial of service. No public POC was provided, and the narrow page-boundary requirement (AC:H) makes reliable triggering difficult.