CVE-2026-89726

A flaw was found in the Linux kernel's ucs2_strnlen() function. This vulnerability occurs because the function checks the current character before verifying if the maximum allowed length has been reached. If the input string is not properly terminated within the specified bounds, an attacker could potentially trigger an out-of-bounds read, which may lead to information disclosure or a denial of service.

A MODERATE severity out-of-bounds read flaw was found in the Linux kernel's ucs2_strnlen() function in lib/ucs2_string.c. The function checks the current character before verifying that the caller-provided maximum length has been reached, so input that is not NUL-terminated within that bound causes the loop to read one ucs2_char_t past the limit. A local attacker with low privileges who can supply such input to a kernel code path that calls ucs2_strnlen() could use this flaw to trigger a kernel panic, resulting in a denial of service. Red Hat rated this flaw as MODERATE (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H), reflecting availability impact only. The kernel and kernel-rt packages in Red Hat Enterprise Linux 7, 8, 9, and 10 update streams and the kernel embedded in the Red Hat Enterprise Linux CoreOS images used by OpenShift Container Platform are affected; Red Hat Enterprise Linux 6 is not affected because the vulnerable code is not present in that stream. Because this flaw is MODERATE with a CVSS score below 7.0, fixes for the affected Red Hat products are deferred rather than delivered through immediate updates, leaving a residual risk of local denial of service on affected systems.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.