CVE-2026-31710 Linux CVE debrief

Who should care

Linux kernel maintainers, users, and administrators, especially those using SMB1 UNIX mounts, should assess exposure and apply patches to prevent potential issues with directory path handling.

Why it matters

CVE-2026-31710 is a medium-severity vulnerability in the Linux kernel affecting SMB1 UNIX mounts. It requires verification of directory path handling and patch application to prevent unexpected behavior.

• Verify directory path handling in SMB1 UNIX mounts to prevent unexpected behavior.
• Assess and apply patches for Linux kernel versions 7.0.1 to 7.0.2 to ensure proper fix.
• Monitor for potential issues with directory paths in Linux kernel environments.

Technical summary

The Linux kernel vulnerability (CVE-2026-31710) was resolved, affecting SMB1 UNIX mounts. The issue was caused by the incorrect dir separator used in paths due to missing CIFS_MOUNT_POSIX_PATHS bit in cifs_sb_info::mnt_cifs_flags. This could lead to unexpected behavior when handling directory paths. The vulnerability was introduced due to the incorrect handling of cifs_sb->mnt_cifs_flags in cifs_mount_get_tcon() with SMB1 UNIX mounts. The issue was resolved by ensuring that @cifs_sb->mnt_cifs_flags is read or updated after calling reset_cifs_unix_caps().

Defensive priority

Medium priority for Linux kernel maintainers and users, especially those using SMB1 UNIX mounts, to assess and apply patches.

Recommended defensive actions

• Assess exposure and apply patches for Linux kernel versions 7.0.1 to 7.0.2.
• Review and update SMB1 UNIX mounts configurations to ensure proper handling of directory paths.
• Monitor for potential unexpected behavior in directory path handling.
• Verify directory path handling in SMB1 UNIX mounts to prevent unexpected behavior.
• Assess and apply patches for Linux kernel versions 7.0.1 to 7.0.2 to ensure proper fix.
• Monitor for potential issues with directory paths in Linux kernel environments.
• Review compensating controls for exposed systems while remediation is scheduled and verified.

Evidence notes

The vulnerability was introduced due to the incorrect handling of cifs_sb->mnt_cifs_flags in cifs_mount_get_tcon() with SMB1 UNIX mounts. The issue was resolved by ensuring that @cifs_sb->mnt_cifs_flags is read or updated after calling reset_cifs_unix_caps().

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.