btrfs: fix reloc root cleanup in merge_reloc_roots() (CVE-2026-93798) | HOL Guard CVE

High · CVSS 7.8CVE-2026-93798

btrfs: fix reloc root cleanup in merge_reloc_roots()

Answer in brief

CVE-2026-93798 records a High severity (CVSS 7.8) vulnerability in btrfs: fix reloc root cleanup in merge_reloc_roots(). The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 24, 2026Updated Sep 25, 2026Source checked Sep 25, 2026First seen by HOL Sep 25, 2026Material review Sep 25, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 7.8
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 7.8. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Linux/Linuxgeneric	>=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <ab48583aa9948205ff9a6470e23dbff74c565e24 \|\| >=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <63d6b1f04cd91c825329712aa526215ffa5d11ca \|\| >=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <b78fe9563e2d5ae47805f1e5dc722c91fd30e1f8 \|\| >=0 <6.12.111 \|\| >=0 <6.18.53	ab48583aa9948205ff9a6470e23dbff74c565e24, 63d6b1f04cd91c825329712aa526215ffa5d11ca, b78fe9563e2d5ae47805f1e5dc722c91fd30e1f8, 6.12.111, 6.18.53

Recommended response

Check inventory. Check lockfiles and deployed manifests for Linux/Linux.
Review the reported fix. Update Linux/Linux to ab48583aa9948205ff9a6470e23dbff74c565e24 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 24, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 25, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 25, 2026

Sources and claim methodology

Upstream source description

In the Linux kernel, the following vulnerability has been resolved: btrfs: fix reloc root cleanup in merge_reloc_roots() If the root we got has zero root refs in its root item, we are resetting the root's ->reloc_root without using barriers like we do everywhere else. Sashiko complained about this while reviewing another patch, and it's correct (see the Link tag below). Also, we should not clear BTRFS_ROOT_DEAD_RELOC_TREE from the root unless the root points to the reloc root we have. Fix this by using clear_reloc_root(), which issues the memory barrier after setting the root's ->reloc_root to NULL and before clearing the bit BTRFS_ROOT_DEAD_RELOC_TREE from the root.

Quoted source text, attributed separately from HOL analysis.