CVE-2014-9710

What it actually does

Race condition in Btrfs xattr replacement allows local users to bypass ACL consistency checks and gain privileges via standard filesystem operations during the replacement time window or after a failed replacement.

Why it matters to the business

Local attackers on affected Linux systems can escalate privileges to root, resulting in full host compromise; the issue is historical with low current exploitability but still requires kernel updates on legacy deployments.

How an attack unfolds

An attacker with local shell access performs concurrent filesystem operations targeting extended attributes on a Btrfs volume to exploit the window where visible xattr state diverges from the requested replacement, ultimately bypassing ACL enforcement and obtaining elevated privileges.

How to fix it

Upgrade the Linux kernel to version 3.19 or newer; apply all subsequent security backports if running a distribution kernel; disable Btrfs if unused on legacy systems.

How to confirm the fix worked

Verify running kernel version is 3.19 or later via uname -r; confirm Btrfs xattr behavior matches expected ACL enforcement through targeted filesystem tests.

Typical attack path

1. Obtain local unprivileged shell on target host
2. Identify Btrfs-mounted filesystems
3. Trigger concurrent xattr set/replace operations to hit the race window
4. Bypass ACL checks and execute privileged actions

How to detect it

Review system logs for unusual xattr modification patterns or unexpected privilege changes around Btrfs operations; correlate with authentication and process execution events indicating local escalation attempts.

What your security team should do

• Prioritize kernel upgrades on any remaining systems running kernels before 3.19
• Remove Btrfs usage where feasible on unpatched hosts
• Audit local user accounts and filesystem permissions for signs of prior misuse