# CVE-2026-45915: fat: avoid parent link count underflow in rmdir

Status: published. Published: 2026-05-27. Updated: 2026-11-06.

In the Linux kernel, the following vulnerability has been resolved:

fat: avoid parent link count underflow in rmdir

Corrupted FAT images can leave a directory inode with an incorrect
i_nlink (e.g. 2 even though subdirectories exist). rmdir then
unconditionally calls drop_nlink(dir) and can drive i_nlink to 0,
triggering the WARN_ON in drop_nlink().

Add a sanity check in vfat_rmdir() and msdos_rmdir(): only drop the
parent link count when it is at least 3, otherwise report a filesystem
error.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- Linux / Linux: ≥ 9a53c3a783c2fa9b969628e65695c11c3e51e673; < 7fe0de287e931e07cb96ecf1f449b2ebdb0e1115 (affected, git); ≥ 9a53c3a783c2fa9b969628e65695c11c3e51e673; < 9894c79fd9466612d0514be157b5c30cd93aa645 (affected, git); ≥ 9a53c3a783c2fa9b969628e65695c11c3e51e673; < cd569b87378b9c33ae13c23d6bb9d205d66f7c4b (affected, git); ≥ 9a53c3a783c2fa9b969628e65695c11c3e51e673; < d3b7ffa90f613938128432c7b2f35b7aa4bdd86b (affected, git); ≥ 9a53c3a783c2fa9b969628e65695c11c3e51e673; < 955c5d670b5ae07c78f4345e23a895638db96ce1 (affected, git); ≥ 9a53c3a783c2fa9b969628e65695c11c3e51e673; < 17866f8a0822d414cb02e621cf003a7d04396ef8 (affected, git); ≥ 9a53c3a783c2fa9b969628e65695c11c3e51e673; < d0bb592fa9def2bace90ac8926c0a1d6fa8c1aa0 (affected, git); ≥ 9a53c3a783c2fa9b969628e65695c11c3e51e673; < 8cafcb881364af5ef3a8b9fed4db254054033d8a (affected, git). Source: CNA: Linux
- Linux / Linux: 2.6.19 (affected); ≥ 0; < 2.6.19 (unaffected, semver); ≥ 5.10.252; ≤ 5.10.* (unaffected, semver); ≥ 5.15.202; ≤ 5.15.* (unaffected, semver); ≥ 6.1.165; ≤ 6.1.* (unaffected, semver); ≥ 6.6.128; ≤ 6.6.* (unaffected, semver); ≥ 6.12.75; ≤ 6.12.* (unaffected, semver); ≥ 6.18.14; ≤ 6.18.* (unaffected, semver); ≥ 6.19.4; ≤ 6.19.* (unaffected, semver); ≥ 7.0; ≤ * (unaffected, original_commit_for_fix). Source: CNA: Linux

## Severity and prioritization

- CISA KEV: No listing in collected sources

- EPSS: 0.16% as of 2026-11-06; percentile 5.27%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: Not reported

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://git.kernel.org/stable/c/7fe0de287e931e07cb96ecf1f449b2ebdb0e1115 (CNA: Linux)

- https://git.kernel.org/stable/c/9894c79fd9466612d0514be157b5c30cd93aa645 (CNA: Linux)

- https://git.kernel.org/stable/c/cd569b87378b9c33ae13c23d6bb9d205d66f7c4b (CNA: Linux)

- https://git.kernel.org/stable/c/d3b7ffa90f613938128432c7b2f35b7aa4bdd86b (CNA: Linux)

- https://git.kernel.org/stable/c/955c5d670b5ae07c78f4345e23a895638db96ce1 (CNA: Linux)

- https://git.kernel.org/stable/c/17866f8a0822d414cb02e621cf003a7d04396ef8 (CNA: Linux)

- https://git.kernel.org/stable/c/d0bb592fa9def2bace90ac8926c0a1d6fa8c1aa0 (CNA: Linux)

- https://git.kernel.org/stable/c/8cafcb881364af5ef3a8b9fed4db254054033d8a (CNA: Linux)

## Provenance

- CNA: Linux: https://www.cve.org/CVERecord?id=CVE-2026-45915; retrieved 2026-11-06; source updated 2026-11-06

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-45915; retrieved 2026-11-06; source updated Not reported

Revision: de0f7fee8944d8a3136174a2536c57ce90b1524fc249d121b4a15cf473dbdd1a

Canonical: https://y2.dev/cve/CVE-2026-45915

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Collected public records only. Check source status for coverage and freshness.