CVE-2026-53122 Linux CVE debrief

Who should care

Linux system administrators, kernel maintainers, and users of btrfs file systems should assess their exposure and apply patches or mitigations as necessary. They should review system configurations and kernel versions, monitor system logs for signs of deadlocks or hangs, and consider disabling the flushoncommit mount option if not required.

Why it matters

CVE-2026-53122 is a medium-severity vulnerability in the Linux kernel's btrfs module. It can cause deadlocks when using the flushoncommit mount option, potentially leading to system hangs or availability impacts. Linux system administrators and users of btrfs file systems should assess their exposure and apply patches or mitigations as necessary.

• System hangs or unresponsiveness due to deadlocks.
• Potential data loss or corruption if deadlocks occur during critical operations.
• Increased risk of denial-of-service (DoS) attacks.
• Need for verification of affected versions and patch application.

Technical summary

The vulnerability exists in the Linux kernel's btrfs module when using the flushoncommit mount option. A deadlock can occur between a transaction commit and a reflink operation that copies an inline extent to an offset beyond the current i_size of the destination node. This issue can cause system hangs or other availability impacts. The deadlock happens when a transaction commit and a reflink operation are executed concurrently. The vulnerability was reported by syzbot and is caused by a deadlock between a transaction commit and a reflink operation in btrfs when using the flushoncommit mount option.

Defensive priority

Medium priority should be given to assessing exposure and applying patches, as the vulnerability can cause a deadlock, potentially leading to system hangs or other availability impacts.

Recommended defensive actions

• Assess exposure by reviewing system configurations and kernel versions.
• Apply patches from Linux kernel maintainers.
• Monitor system logs for signs of deadlocks or hangs.
• Consider disabling flushoncommit mount option if not required.
• Review compensating controls for exposed systems while remediation is scheduled and verified.
• Check relevant monitoring, detection, and logs for exposed assets that need extra review.
• Track exceptions, retest remediated assets, and close the item only after evidence is documented.

Evidence notes

The vulnerability was reported by syzbot and is caused by a deadlock between a transaction commit and a reflink operation in btrfs when using the flushoncommit mount option. The issue arises when a reflink operation copies an inline extent to an offset beyond the current i_size of the destination node, and a transaction commit attempts to flush delalloc, leading to a deadlock.

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.