CVE-2026-23249

MEDIUM EPSS 3.8%
Published Mar 18, 20263mo ago · Modified Jun 17, 20261w ago
5.5 CVSS 3.1
Medium
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Published Mar 18, 2026 3mo ago
Last Modified Jun 17, 2026 1w ago

Description

In the Linux kernel, the following vulnerability has been resolved: xfs: check for deleted cursors when revalidating two btrees The free space and inode btree repair functions will rebuild both btrees at the same time, after which it needs to evaluate both btrees to confirm that the corruptions are gone. However, Jiaming Zhang ran syzbot and produced a crash in the second xchk_allocbt call. His root-cause analysis is as follows (with minor corrections): In xrep_revalidate_allocbt(), xchk_allocbt() is called twice (first for BNOBT, second for CNTBT). The cause of this issue is that the first call nullified the cursor required by the second call. Let's first enter xrep_revalidate_allocbt() via following call chain: xfs_file_ioctl() -> xfs_ioc_scrubv_metadata() -> xfs_scrub_metadata() -> `sc->ops->repair_eval(sc)` -> xrep_revalidate_allocbt() xchk_allocbt() is called twice in this function. In the first call: /* Note that sc->sm->sm_type is XFS_SCRUB_TYPE_BNOPT now */ xchk_allocbt() -> xchk_btree() -> `bs->scrub_rec(bs, recp)` -> xchk_allocbt_rec() -> xchk_allocbt_xref() -> xchk_allocbt_xref_other() since sm_type is XFS_SCRUB_TYPE_BNOBT, pur is set to &sc->sa.cnt_cur. Kernel called xfs_alloc_get_rec() and returned -EFSCORRUPTED. Call chain: xfs_alloc_get_rec() -> xfs_btree_get_rec() -> xfs_btree_check_block() -> (XFS_IS_CORRUPT || XFS_TEST_ERROR), the former is false and the latter is true, return -EFSCORRUPTED. This should be caused by ioctl$XFS_IOC_ERROR_INJECTION I guess. Back to xchk_allocbt_xref_other(), after receiving -EFSCORRUPTED from xfs_alloc_get_rec(), kernel called xchk_should_check_xref(). In this function, *curpp (points to sc->sa.cnt_cur) is nullified. Back to xrep_revalidate_allocbt(), since sc->sa.cnt_cur has been nullified, it then triggered null-ptr-deref via xchk_allocbt() (second call) -> xchk_btree(). So. The bnobt revalidation failed on a cross-reference attempt, so we deleted the cntbt cursor, and then crashed when we tried to revalidate the cntbt. Therefore, check for a null cntbt cursor before that revalidation, and mark the repair incomplete. Also we can ignore the second tree entirely if the first tree was rebuilt but is already corrupt. Apply the same fix to xrep_revalidate_iallocbt because it has the same problem.

CVSS Details

Base Score
5.5
Exploitability
1.8
Impact
3.6
Vector string
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Attack Vector Local
Attack Complexity Low
Privileges Required Low
User Interaction None
Scope Unchanged
Confidentiality None
Integrity None
Availability High

Threat Intelligence

EPSS Exploit Probability
3.8% percentile
Exploit & Patch Status
No Known Exploit
Patch Available

Weaknesses 1

CWE-476 NULL Pointer Dereference Memory Safety

Affected Products 3

VendorProductVersionRange
linuxlinux_kernel*≥6.8  –  <6.12.75
linuxlinux_kernel*≥6.13  –  <6.18.16
linuxlinux_kernel*≥6.19  –  <6.19.6

References 4

  • git.kernel.org https://git.kernel.org/stable/c/55e03b8cbe2783ec9acfb88e8adb946ed504e117
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/5991e96f2ae82df60a3e4ed00f3432d9f3502a99
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/b04baa848c0543b240b1bd8aecff470382f6f154
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/d69de525bc7ab27713342080bf50826df3f6a68f
    Patch

Remediation

  • git.kernel.org https://git.kernel.org/stable/c/55e03b8cbe2783ec9acfb88e8adb946ed504e117
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/5991e96f2ae82df60a3e4ed00f3432d9f3502a99
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/b04baa848c0543b240b1bd8aecff470382f6f154
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/d69de525bc7ab27713342080bf50826df3f6a68f
    Patch