CVE-2025-71123 Linux CVE debrief

Who should care

System administrators and users of Linux-based systems, particularly those using ext4 filesystem, should be aware of this vulnerability. Applying the provided patches or updating to a fixed kernel version is recommended to prevent potential exploitation.

Technical summary

The vulnerability is caused by the use of strscpy_pad() to copy a non-NUL-terminated string into a NUL-terminated string of possibly larger size. The function parse_apply_sb_mount_options() in fs/ext4/super.c uses a 64-byte buffer to store the s_mount_opts field, which is expected to be at most 63 characters long with a NUL terminator. If a longer non-NUL-terminated string is provided, strscpy_pad() can overflow the buffer, leading to a buffer overflow warning. The fix is to use a 64-byte buffer that matches the size of s_mount_opts and return an error if the user provides a non-NUL-terminated string.

Defensive priority

High

Recommended defensive actions

• Apply patches provided by the Linux kernel maintainers
• Update to a fixed kernel version
• Monitor system logs for buffer overflow warnings
• Restrict user input to prevent non-NUL-terminated strings
• Implement compensating controls, such as SELinux or AppArmor, to limit the impact of potential exploitation

Evidence notes

The vulnerability was found by the Linux Verification Center (linuxtesting.org) with Syzkaller. The CVE record was published on 2026-01-14T15:16:02.000Z and last modified on 2026-07-14T13:18:03.980Z. The NVD entry is currently Modified.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.