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CVE-2026-68154
libceph: reject zero bucket types in crush_decode
Published 2026-08-10 (2 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-2026-68154 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 | fixed | 6.12.101-1 | Update the kernel and reboot. Fixed in 6.12.101-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.6-1 | Update the kernel and reboot. Fixed in 7.1.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.6-1 | Update the kernel and reboot. Fixed in 7.1.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4745-1 · 2026-08-18 · text | 6.12.101-1~deb12u1 | Update the kernel and reboot. DLA-4745-1 shipped the fix on 2026-08-18, in 6.12.101-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
CRUSH bucket type 0 is reserved for devices. The mapper relies on that invariant and uses type 0 to identify leaf devices. If crush_decode() accepts a bucket with type 0, a malformed CRUSH map can make the mapper treat a negative bucket ID as a device and pass it to is_out(), which then indexes the OSD weight array with a negative value. Reject zero bucket types while decoding the CRUSH map so the invalid state never reaches the mapper.
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 libcephPrints 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
- 2026-08-10 (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
- 0.71%, higher than 52.8% 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 |
|---|---|---|
| 2.6.34 | 5.10.265 | 952ca5dc9991 |
| 2.6.34 | 5.15.216 | 146461f09565 |
| 2.6.34 | 6.1.183 | 80fc40e11cda |
| 2.6.34 | 6.6.148 | b8a9fb6bf806 |
| 2.6.34 | 6.12.101 | 826cd1de5802 |
| 2.6.34 | 6.18.42 | 3b2f1937f5fc |
| 2.6.34 | 7.1.6 | 70998f91030e |
| 2.6.34 | 7.2 | 05f902842233 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4777-1 | 2026-09-08 | bookworm 6.1.187-1 | tracker |
| DLA-4745-1 | 2026-08-18 | bookworm 6.12.101-1~deb12u1 | 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 flaw is reached when the in-kernel Ceph client decodes a crafted CRUSH map inside CEPH_MSG_OSD_MAP received over TCP from a Ceph monitor or OSD, which is a standard network-delivered cluster control message on connected storage clients.
- AC:LAttack complexity, low
- An attacker can reliably craft a CRUSH map with a bucket whose type field is zero and controlled hierarchy/items so crush_do_rule() later calls is_out() with a negative index, without races, victim-specific memory layout, or rare kernel build options.
- PR:NPrivileges required, none
- No local privileges on the victim host are required; a remote attacker who controls, compromises, or MITMs the authenticated Ceph monitor/OSD peer can deliver the malicious OSD map over the established client cluster connection.
- UI:NUser interaction, none
- No additional victim action is needed at exploit time because poisoned OSD maps are processed automatically and CRUSH placement is recalculated during routine map updates, request rescanning, and normal Ceph client I/O.
- S:UScope, unchanged
- The vulnerability corrupts or reads kernel memory on the host running the Ceph client, affecting that kernel security domain rather than crossing a VM, container sandbox, or IOMMU boundary.
- C:HConfidentiality impact, high
- When a type-0 bucket makes the mapper treat a negative bucket ID as a device, is_out() indexes osd_weight[] with a negative value, causing an out-of-bounds read of adjacent kernel memory beyond the OSD weight array.
- I:HIntegrity impact, high
- This out-of-bounds kernel heap access during CRUSH placement is memory corruption in a privileged parser/mapper path that can be leveraged for further kernel memory control and arbitrary code execution, not only information disclosure.
- A:HAvailability impact, high
- The invalid negative indexing during CRUSH mapping can dereference unmapped or non-resident memory and trigger a kernel oops or panic, causing complete loss of availability on affected Ceph client hosts.