CVE-2026-68082

What the bug is

decode_lockers() in cls_lock_client.c contains two bare decode operations that allow a malicious or compromised OSD to trigger slab-out-of-bounds reads: 1. ceph_decode_32(p) at the num_lockers field has no preceding bounds check. ceph_start_decoding() accepts struct_len=0 as valid -- the internal ceph_decode_need(p, end, 0, bad) always passes -- so when an OSD sends struct_len=0, ceph_start_decoding() returns success with p == end. The immediately following bare ceph_decode_32(p) then reads 4 bytes past the validated buffer boundary. The garbage value is passed directly to kzalloc_objs() as the locker count. The sibling function decode_watchers() in osd_client.c already uses ceph_decode_32_safe() after its own ceph_start_decoding() call. decode_lockers() was the only site using the bare variant. 2. ceph_decode_8(p) after the decode_locker() loop has no preceding bounds check. If an OSD crafts num_lockers such that the loop advances p exactly to end, the subsequent bare ceph_decode_8(p) reads one byte past the validated buffer boundary. The result is passed directly into *type, which is used as a lock type discriminator by callers, giving an OSD-controlled one-byte OOB read with direct influence over the lock type field. Fix both by replacing bare operations with their safe variants: ceph_decode_32(p) -> ceph_decode_32_safe(p, end, *num_lockers, err_inval) ceph_decode_8(p) -> ceph_decode_8_safe(p, end, *type, err_free_lockers) The goto targets differ intentionally: err_inval: is a new label returning -EINVAL directly. It is used for the pre-allocation failure path where *lockers is not yet allocated and must not be passed to ceph_free_lockers(). err_free_lockers: is the existing label. It is used for the post-allocation failure path where *lockers is allocated and must be freed. ret is set to -EINVAL before ceph_decode_8_safe() so that err_free_lockers returns the correct error code on bounds violation. Without this, err_free_lockers would return a stale ret value (0 from the successful decode_locker() loop), silently swallowing the error. -EINVAL is correct for both failure paths. The data received from the OSD is structurally malformed. -ENOMEM would misrepresent the failure class to callers and to stable@ backporters triaging error paths. Attacker model: a malicious or compromised OSD in a multi-tenant Ceph deployment can trigger this against any kernel client that issues the lock.get_info class method (e.g. during RBD exclusive lock acquisition). [ idryomov: trim changelog, formatting ]

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.

net/ceph/cls_lock_client.c

What this is

CEPH COMMON CODE (LIBCEPH)MAINTAINERS section matched on net/ceph/ · ceph-devel@vger.kernel.org · Supported

Kernel module

libceph

Check it on the machine

grep -w CONFIG_CEPH_LIB /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 libceph

Prints 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_CEPH_LIB

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

2026-08-08 (2 months ago)source

CVSS

9.8 critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsource recompute it

Attack vector

network (AV:N)source

EPSS

0.40%, higher than 32.6% of all CVEssource

CISA KEV

not listedthe KEV catalogue

Debian urgency

not yet assignedsource

Subsystem

net/ceph

Upstream fixes

The versions the CNA records as introducing and fixing this, and the commit for each. source

Introduced	Fixed in	Commit
4.9	5.10.266	c8ade01170a2
4.9	5.15.217	001835c59989
4.9	6.1.184	7c422364acd9
4.9	6.6.153	02430f6f729b
4.9	6.12.105	57ba829804fe
4.9	6.18.46	89df5d71f83f
4.9	7.1.6	a54be593d0b7
4.9	7.2	a109a5561152

Debian advisories