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CVE-2026-52960
ceph: put folios not suitable for writeback
Published 2026-06-24 (4 months ago) by the Linux kernel CNA. Subsystem fs/ceph. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-52960 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 | not affected | 6.1.190-1 | Nothing to do. bookworm never shipped the vulnerable code. |
| Debian 13trixie | not affected | 6.12.113-1 | Nothing to do. trixie never shipped the vulnerable code. |
| Debian 14forky | fixed | 7.0.10-1 | Update the kernel and reboot. Fixed in 7.0.10-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.10-1 | Update the kernel and reboot. Fixed in 7.0.10-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
The batch holds references to the folios (see `filemap_get_folios`, `folio_batch_release`), so we need to `folio_put` the folios we remove. Tested on v6.18.
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/ceph/addr.c
- What this is
- CEPH DISTRIBUTED FILE SYSTEM CLIENT (CEPH)MAINTAINERS section matched on fs/ceph/ · ceph-devel@vger.kernel.org · Supported
- Kernel module
- ceph
Check it on the machine
grep -w CONFIG_CEPH_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 cephPrints 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, sidm
- m
- a loadable module on every flavour - check lsmod, can be blacklisted
- Build switch
- CONFIG_CEPH_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
- 2026-06-24 (4 months ago)source
- CVSS
- 7.5 high
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Hsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.61%, higher than 48.1% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- fs/ceph
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.15 | 6.18.57 | 349499a65b6b |
| 6.15 | 7.0.10 | 86921e890fe1 |
| 6.15 | 7.1 | 544576f0f05c |
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:NAttack vector, network
- Direct reachability is through CephFS file writeback, and a writable CephFS tree can reasonably be exposed through kernel network fileservers such as nfsd/ksmbd, which drive the same VFS writeback path remotely.
- AC:LAttack complexity, low
- The bug is a deterministic missing folio_put() on skipped writeback folios; an attacker can repeatedly create/write/delete/sync files to accumulate leaked references without needing an uncontrollable race.
- PR:NPrivileges required, none
- In the network-export scenario, the attacker needs no local privileges on the vulnerable host, and writable anonymous or guest-style exports are a reasonable high-severity deployment.
- UI:NUser interaction, none
- Once the CephFS mount/export exists, exploitation only requires attacker-driven writes and writeback triggers; no victim user action is needed.
- S:UScope, unchanged
- The impact remains within the vulnerable kernel host and does not cross a separate security authority such as a guest-to-host or IOMMU boundary.
- C:NConfidentiality impact, none
- The flaw leaks folio references and pins page-cache memory; it does not provide an information disclosure or arbitrary read primitive.
- I:NIntegrity impact, none
- The flaw does not corrupt memory or allow unauthorized data modification; it only prevents selected folios from being released.
- A:HAvailability impact, high
- Repeated triggering can leave folios permanently unreclaimable even after unmount/drop_caches, causing severe memory pressure, swapping, allocation failures, and potential system-wide DoS.