CVE-2026-98245
Received Received - Intake

Btrfs Use-After-Free in mark_block_group_to_copy

Publication date: 2026-10-06

Last updated on: 2026-10-06

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: btrfs: take commit root semaphore when iterating in mark_block_group_to_copy() mark_block_group_to_copy() iterates over the commit root with skip_locking=true. A concurrent transaction commit can swap and free the commit root during iteration, causing use-after-free when accessing extent buffers. Fix it by using path->need_commit_sem to protect the commit root search.

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Meta Information

Published
2026-10-06
Last Modified
2026-10-06
Generated
2026-10-06
AI Q&A
2026-10-06
EPSS Evaluated
N/A
NVD
CVE-2026-98245
EUVD
EUVD-2026-93173

Affected Vendors & Products

Showing 5 associated CPEs
Vendor Product Version / Range
Linux Linux 78ce9fc269af6e69c1399ab910ba6bc81c934f67
Linux Linux 78ce9fc269af6e69c1399ab910ba6bc81c934f67
Linux Linux 78ce9fc269af6e69c1399ab910ba6bc81c934f67
Linux Linux 78ce9fc269af6e69c1399ab910ba6bc81c934f67
Linux Linux 5.12

Helpful Resources

Exploitability

CWE
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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This is a use-after-free vulnerability in the Linux kernel's Btrfs filesystem. It occurs when mark_block_group_to_copy() iterates over the commit root without proper locking. A concurrent transaction commit can free the commit root during iteration, leading to a use-after-free when accessing extent buffers.

Detection Guidance

This vulnerability is specific to the Linux kernel's btrfs filesystem and requires kernel-level inspection. Detection involves checking kernel logs for btrfs-related errors or crashes, particularly during filesystem operations. Use commands like 'dmesg | grep btrfs' or 'journalctl -k | grep btrfs' to search for related errors. If you suspect exploitation, monitor for unexpected system freezes or data corruption during btrfs operations.

Impact Analysis

This vulnerability could cause system crashes, data corruption, or potential privilege escalation if exploited. Systems using Btrfs filesystem with concurrent transactions may be affected.

Mitigation Strategies

Immediate mitigation requires updating the Linux kernel to a patched version that includes the fix for CVE-2026-98245. Check your distribution's security updates and apply them promptly. If updating is not immediately possible, avoid using btrfs features that involve concurrent transactions or block group operations until patched.

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