Vulnerability in Linux kernel (CVE-2026-80537)
Summary
Vulnerability in Linux kernel (CVE-2026-80537). Successful exploitation can lead to full system takeover.
Original description
The description as published by the source.
In the Linux kernel, the following vulnerability has been resolved:
xfs: fix off-by-one in rtrefcount btree root level validation
xfs_rtrefcountbt_compute_maxlevels() sets
mp->m_rtrefc_maxlevels = min(d_maxlevels, r_maxlevels) + 1;
where the trailing "+ 1" already accounts for the inode-root level, so the
deepest valid on-disk root level is m_rtrefc_maxlevels - 1 and a cursor must
satisfy bc_nlevels <= bc_maxlevels (= m_rtrefc_maxlevels).
The two on-disk validation paths, xfs_rtrefcountbt_verify() and
xfs_iformat_rtrefcount(), check the root level with ">" instead of ">=", so a
crafted rtreflink (metadir + realtime + reflink) image whose
/rtgroups/N.refcount inode has bb_level == m_rtrefc_maxlevels is accepted on
mount. xfs_rtrefcountbt_init_cursor() then sets bc_nlevels = bb_level + 1,
exceeding bc_maxlevels by one. Since the xfs_rtrefcountbt_cur slab object is
sized for exactly bc_maxlevels entries, the first btree op on such a cursor
indexes bc_levels[m_rtrefc_maxlevels] past the end of the object. This is
reached by the first rtrefcount cursor built after mount, via log/CoW
recovery (xfs_reflink_recover_cow() during xfs_mountfs()) or an
FS_IOC_GETFSMAP over the realtime device.
Reject a root level equal to m_rtrefc_maxlevels, matching the ">=" form
already used by the sibling data-device refcount/rmap verifiers and the
in-memory rtrmap verifier.
BUG: KASAN: slab-out-of-bounds in xfs_btree_lookup (fs/xfs/libxfs/xfs_btree.c:2101)
Write of size 2 at addr ffff8880…
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-80537 has been found in Linux kernel.
Successful exploitation can lead to full system takeover. CVSS score: 7.8/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Linux kernel CVE-2026-80537" on the vendor's site.
CVE-2026-80537 (Linux kernel) — CVSS v3 7.8
Attack vector: local / no user interaction
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (unclassified) exists in Linux kernel.
Check the vendor advisory for the affected versions of Linux kernel.
Severity: High (CVSS 7.8/10). Successful exploitation can lead to full system takeover.
Update to the patched release per vendor advisory.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
Audit SBOM/dependencies for affected components.資産台帳・SBOM・依存マニフェストで Linux kernel を使っているサービスとバージョンを洗い出す。
-
2Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
Fix status by distribution
Fixed packages published by each distribution for this CVE
- BellSoft Alpaquita BELL-CVE-2026-80537 linux-lts Fixed in: 6.18.46-r0
- Debian DEBIAN-CVE-2026-80537 linux Fixed in: 7.1.10-1
- Ubuntu UBUNTU-CVE-2026-80537 linux-hwe-edge
References
- advisory nvd.nist.gov
- advisory github.com
- package git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web github.com