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CVE-2026-80536
xfs: bounds-check buffer log item's dirty bitmap
Published 2026-08-26 (2 months ago) by the Linux kernel CNA. Subsystem fs/xfs. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-80536 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | fixedDLA-4777-1 · 2026-09-08 · text | 6.1.187-1 | Update the kernel and reboot. DLA-4777-1 shipped the fix on 2026-09-08, in 6.1.187-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixedDSA-6477-1 · 2026-08-29 · text | 6.12.107-1 | Update the kernel and reboot. DSA-6477-1 shipped the fix on 2026-08-29, in 6.12.107-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.10-1 | Update the kernel and reboot. Fixed in 7.1.10-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.10-1 | Update the kernel and reboot. Fixed in 7.1.10-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4788-1 · 2026-09-19 · text | 6.12.107-1~deb12u1 | Update the kernel and reboot. DLA-4788-1 shipped the fix on 2026-09-19, in 6.12.107-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
xlog_recover_do_reg_buffer() replays each dirty region described by a buffer log item's bitmap into the buffer read for that item: memcpy(xfs_buf_offset(bp, (uint)bit << XFS_BLF_SHIFT), item->ri_buf[i].iov_base, nbits << XFS_BLF_SHIFT); The destination offset (bit/nbits, from the logged dirty bitmap) and the buffer size (from the logged blf_len) are both attacker-controlled and otherwise unrelated, yet the only thing bounding the copy is an ASSERT(), which compiles away on production kernels. A crafted image logging a small blf_len together with a bitmap bit past the end of that buffer drives the memcpy() past the buffer's allocation, corrupting adjacent kernel heap during mount-time log recovery. This is reachable by anyone who can get a crafted image mounted -- the malicious-filesystem threat model XFS already guards against elsewhere. Turn the ASSERT() into a real XFS_IS_CORRUPT() check that aborts recovery of the buffer with -EFSCORRUPTED, consistent with the validate-and-fail idiom already used in xlog_recover_do_inode_buffer() and xfs_dquot_item_recover.c. xlog_recover_do_reg_buffer() therefore becomes STATIC int and its three callers propagate the error. Found and confirmed with KASAN on a CONFIG_XFS_DEBUG=n build: the crafted image trips a slab-out-of-bounds write before this change and fails recovery cleanly with -EFSCORRUPTED after it.
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
fs/xfs/xfs_buf_item_recover.c
- What this is
- XFS FILESYSTEMMAINTAINERS section matched on fs/xfs/ · linux-xfs@vger.kernel.org · Supported
- Kernel module
- xfs
Check it on the machine
grep -w CONFIG_XFS_FS /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
lsmod | grep -w xfsPrints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.
Show whether Debian builds this, per release
Debian builds this as a loadable module. Every release below compiles it as a module on every flavour, so whether the code is in the running kernel depends on whether that module is loaded.
- bookworm, trixie, forky, sid, bookworm · linux-6.12m
- m
- a loadable module on every flavour - check lsmod, can be blacklisted
- Build switch
- CONFIG_XFS_FS
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-08-26 (2 months ago)source
- CVSS
- 8.4 high
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.14%, higher than 3.1% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- fs/xfs
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 2.6.12 | 5.10.267 | acb4e26295e7 |
| 2.6.12 | 5.15.218 | f3859c35a4fb |
| 2.6.12 | 6.1.185 | f7b5fa83e2c1 |
| 2.6.12 | 6.6.154 | b7528b42813f |
| 2.6.12 | 6.12.106 | 7e32d4eebae6 |
| 2.6.12 | 6.18.46 | f8288214459e |
| 2.6.12 | 7.1.10 | edaf5b6bd625 |
| 2.6.12 | 7.2 | 813f8136a2ce |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4788-1 | 2026-09-19 | bookworm 6.12.107-1~deb12u1 | tracker |
| DLA-4777-1 | 2026-09-08 | bookworm 6.1.187-1 | tracker |
| DSA-6477-1 | 2026-08-29 | trixie 6.12.107-1 | tracker |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- The OOB write is only reachable during XFS log recovery at mount time (mount→xfs_mountfs→xfs_log_mount→xlog_recover→xlog_do_recovery_pass pass2→xlog_recover_buf_commit_pass2→xlog_recover_do_reg_buffer); attacker data comes from a local block/loop device image, not from any network protocol handler.
- AC:LAttack complexity, low
- All trigger fields (blf_len, blf_data_map bit/nbits, and logged source bytes in ri_buf) are attacker-authored on-disk log metadata; pairing a small blf_len with a bitmap region past the buffer end deterministically drives memcpy() past the xfs_buf allocation on every mount with no race or uncontrollable layout.
- PR:NPrivileges required, none
- Mounting the crafted image requires no account or capability on the victim host in the malicious-filesystem threat model: an external attacker only supplies removable media or a disk image and desktop/kiosk udisks2 or systemd automount performs the privileged mount on device insertion without attacker credentials.
- UI:NUser interaction, none
- Once the crafted XFS volume is presented to the host, log recovery in xlog_recover_do_reg_buffer() runs automatically during mount (including read-only mounts) before any file access; the attacker needs no separate victim to open files, click links, or perform additional actions beyond presenting the image.
- S:UScope, unchanged
- Heap corruption occurs entirely within the mounting host kernel during log replay; impact is confined to the same kernel security authority and does not cross VM, IOMMU, or container sandbox boundaries.
- C:HConfidentiality impact, high
- KASAN-confirmed slab-out-of-bounds write corrupts adjacent kernel heap objects; such controlled memory corruption is routinely weaponized for arbitrary kernel read primitives and pointer disclosure, not merely a crash.
- I:HIntegrity impact, high
- memcpy() writes attacker-controlled bytes from logged ri_buf regions to attacker-chosen offsets beyond the buffer end, giving a controllable out-of-bounds kernel heap write primitive suitable for control-flow hijacking and privilege escalation.
- A:HAvailability impact, high
- The unchecked memcpy() causes slab-out-of-bounds writes during mount-time recovery (KASAN-verified on CONFIG_XFS_DEBUG=n), reliably corrupting kernel heap and capable of provoking kernel oops/panic or persistent denial of service on repeated mount attempts.