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CVE-2026-72371
afs: Fix the volume AFS_VOLUME_RM_TREE is set on
Published 2026-08-15 (2 months ago) by the Linux kernel CNA. Subsystem fs/afs. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-72371 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 | fixed | 6.1.180-1 | Update the kernel and reboot. Fixed in 6.1.180-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.100-1 | Update the kernel and reboot. Fixed in 6.12.100-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
Fix afs_insert_volume_into_cell() to set AFS_VOLUME_RM_TREE on the volume replaced, not the new volume, as it's now removed from the cell's volume tree. This will cause the old volume to be removed from the tree twice and the new volume never to be removed.
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/afs/volume.c
- What this is
- AFS FILESYSTEMMAINTAINERS section matched on fs/afs/ · linux-afs@lists.infradead.org · Supported
- Kernel module
- kafs
Check it on the machine
grep -w CONFIG_AFS_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 kafsPrints 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, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.
- bookworm, trixie, forky, sidMnot built on amd64/cloud-amd64, arm64/cloud-arm64
- M
- a module where it is built at all; some flavours do not build it
- Build switch
- CONFIG_AFS_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
- 2026-08-15 (2 months ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.18%, higher than 6.6% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- fs/afs
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 5.15.146 | 5.15.212 | 6fa9a8a73e16 |
| 6.1.70 | 6.1.178 | c421bc6b957e |
| 6.6.9 | 6.6.145 | 1607075220cf |
| 6.7 | 6.12.97 | d154c20837f3 |
| 6.7 | 6.18.40 | 158c5a0b1dfc |
| 6.7 | 7.1.5 | d0c8ad418b47 |
| 6.7 | 7.2 | 56b4e4b26f84 |
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 wrong AFS_VOLUME_RM_TREE assignment is only reached from afs_insert_volume_into_cell() during local AFS mount/automount (mount/fsopen→afs_get_tree→afs_validate_fc→afs_create_volume), not from unsolicited inbound RxRPC callback packet handling alone.
- AC:LAttack complexity, low
- An attacker can reliably win the refcount-zero replacement race by running concurrent threads that repeatedly mount or automount the same AFS volume while forcing concurrent teardown/expiry, controlling both the failing afs_try_get_volume() and the rb_replace_node_rcu() path.
- PR:LPrivileges required, low
- Exploitation requires mounting or automounting AFS volumes, available to unprivileged users on typical kAFS clients with world-accessible /afs dynroot/automount paths, or via CAP_SYS_ADMIN inside a user/mount namespace; init-namespace root is not required.
- UI:NUser interaction, none
- No victim interaction is required beyond the attacker (or any local user on the shared kAFS client) issuing the mount/automount and concurrency operations that drive the volume-tree race.
- S:UScope, unchanged
- Impact is kernel heap/RB-tree corruption and use-after-free within the host kernel, enabling standard privilege escalation rather than crossing VM, container, or IOMMU security boundaries.
- C:HConfidentiality impact, high
- Incorrect RM_TREE handling leaves freed afs_volume objects in cell->volumes or corrupts the RB-tree, producing slab use-after-free reads during volume lookups (the same UAF class as the original 9a6b294 race fix).
- I:HIntegrity impact, high
- RB-tree corruption and dangling volume entries provide attacker-influenced heap metadata corruption primitives that can be developed into arbitrary kernel writes or control-flow hijack, not merely a benign error return.
- A:HAvailability impact, high
- The fault causes kernel oops/panic via use-after-free or corrupted RB-tree traversal during volume lookup/removal, and can be retriggered by repeated mount/automount races or subsequent callback-driven lookups.