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CVE-2026-52954

libceph: handle rbtree insertion error in decode_choose_args()

7.5 EPSS 0.5% AV:N

Published 2026-06-24 (4 months ago) by the Linux kernel CNA. Subsystem net/ceph. Debian urgency: not yet assigned.

What to do, per Debian release

Debian's own status for CVE-2026-52954 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-4665-1 · 2026-07-03 · text	6.1.176-1	Update the kernel and reboot. DLA-4665-1 shipped the fix on 2026-07-03, in 6.1.176-1. A running kernel keeps the old code until the machine restarts.
Debian 13trixie	fixed	6.12.94-1	Update the kernel and reboot. Fixed in 6.12.94-1. A running kernel keeps the old code until the machine restarts.
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

A message of type CEPH_MSG_OSD_MAP contains an OSD map that itself contains a CRUSH map. The received CRUSH map may optionally contain choose_args that get decoded in decode_choose_args(). In this function, num_choose_arg_maps is read from the message, and a corresponding number of crush_choose_arg_maps gets decoded afterwards. Each crush_choose_arg_map has a choose_args_index, which serves as the key when inserting it into the choose_args rbtree of the decoded crush_map. If a (potentially corrupted) message contains two crush_choose_arg_maps with the same index, the assertion in insert_choose_arg_map() triggers a kernel BUG when trying to insert the second crush_choose_arg_map. This patch fixes the issue by switching to the non-asserting rbtree insertion function and rejecting the message if the insertion fails. [ idryomov: changelog ]

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/osdmap.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, sidm

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

Debian tracker CVE record NVD kernel CNA record

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: 0.52%, higher than 43.1% 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
4.13	5.10.258	c7bf7864e292
4.13	5.15.209	f47430fc1f81
4.13	6.1.175	0b6a3bcb91bc
4.13	6.6.141	534ebc08df97
4.13	6.12.91	80c73bd1b2b0
4.13	6.18.33	4d2b37abda95
4.13	7.0.10	0a1265a9ab87
4.13	7.1	d289478cfc0b

Debian advisories

Advisory	Date	Shipped to	Debian
DLA-4671-1	2026-07-05	bullseye 6.1.176-1~deb11u1	tracker
DLA-4665-1	2026-07-03	bookworm 6.1.176-1	tracker
DLA-4664-1	2026-07-03	bullseye 5.10.259-1	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:NAttack vector, network: The vulnerable decoder processes CEPH_MSG_OSD_MAP data received over the Ceph network protocol from monitor or OSD peers.
AC:LAttack complexity, low: An attacker controlling an accepted Ceph peer can deterministically include two choose_arg_maps with the same choose_args_index; no race or special memory state is required.
PR:NPrivileges required, none: In the highest reasonable scenario, a malicious or compromised Ceph cluster endpoint sends the malformed map to an already connected client and needs no privileges on the victim system.
UI:NUser interaction, none: OSD map updates are processed asynchronously by the kernel client after the Ceph session exists; no victim action is needed to process the malicious message.
S:UScope, unchanged: The impact is within the same kernel security authority and does not cross a VM, IOMMU, or sandbox boundary.
C:NConfidentiality impact, none: The bug triggers a BUG() assertion on duplicate rbtree insertion and does not provide an information disclosure primitive.
I:NIntegrity impact, none: The vulnerable path does not perform attacker-controlled memory corruption; it aborts via BUG() before creating an integrity-impacting primitive.
A:HAvailability impact, high: The duplicate choose_args_index triggers a kernel BUG/oops in the Ceph client decode path, causing a high-impact denial of service.