CVE-2025-37856: linux

Vulnerability summary

CVE-2025-37856 is a high (CVSS 7.8) vulnerability in linux. EPSS estimates a 0.28% chance of exploitation in the next 30 days, higher than 19.3% of scored vulnerabilities.

Timeline

1. 09-05-2025
   PublishedVulnerability first disclosed.
2. 21-10-2026
   Last modifiedVulnerability information updated.

Description

In the Linux kernel, the following vulnerability has been resolved: btrfs: harden block_group::bg_list against list_del() races As far as I can tell, these calls of list_del_init() on bg_list cannot run concurrently with btrfs_mark_bg_unused() or btrfs_mark_bg_to_reclaim(), as they are in transaction error paths and situations where the block group is readonly. However, if there is any chance at all of racing with mark_bg_unused(), or a different future user of bg_list, better to be safe than sorry. Otherwise we risk the following interleaving (bg_list refcount in parens) T1 (some random op) T2 (btrfs_mark_bg_unused) !list_empty(&bg->bg_list); (1) list_del_init(&bg->bg_list); (1) list_move_tail (1) btrfs_put_block_group (0) btrfs_delete_unused_bgs bg = list_first_entry list_del_init(&bg->bg_list); btrfs_put_block_group(bg); (-1) Ultimately, this results in a broken ref count that hits zero one deref early and the real final deref underflows the refcount, resulting in a WARNING.

No weakness data has been published for this record.