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CVE-2026-68156
libceph: refresh auth->authorizer_buf{,_len} after authorizer update
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-2026-68156 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
ceph_x_create_authorizer() caches au->buf->vec.iov_base and au->buf->vec.iov_len in struct ceph_auth_handshake. These cached values are then used by the messenger connect code when sending the authorizer. ceph_x_update_authorizer() can rebuild the authorizer when a newer service ticket is available. If the rebuilt authorizer no longer fits in the existing buffer, ceph_x_build_authorizer() drops its reference to au->buf and allocates a new one. If this is the final reference, ceph_buffer_put() frees the old ceph_buffer and its vec.iov_base, but auth->authorizer_buf still points at that freed memory. A subsequent msgr1 reconnect can therefore queue the stale pointer and trigger a KASAN slab-use-after-free in _copy_from_iter() while tcp_sendmsg() copies the authorizer. Refresh auth->authorizer_buf and auth->authorizer_buf_len after a successful authorizer rebuild so the messenger sends the current buffer.
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/auth_x.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
- 0.69%, higher than 52.0% 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 |
|---|---|---|
| 3.10 | 5.10.265 | 2334e9997308 |
| 3.10 | 5.15.216 | 79a273df6423 |
| 3.10 | 6.1.183 | 26f814187abc |
| 3.10 | 6.6.148 | 9d37aec9ffe4 |
| 3.10 | 6.12.101 | 75e82e8944ac |
| 3.10 | 6.18.42 | 0060ec912292 |
| 3.10 | 7.1.6 | 5ecfcd5c0586 |
| 3.10 | 7.2 | 937d61f86d37 |
| 3.4.50 | 0 | 0 |
| 3.9.7 | 0 | 0 |
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
- A compromised or malicious Ceph monitor/OSD delivers rotated cephx service tickets over TCP that increase secret_id and can enlarge the authorizer; on subsequent msgr1 reconnect the stale authorizer_buf is copied in tcp_sendmsg, so the UAF is reachable from the network peer without local syscall access.
- AC:LAttack complexity, low
- An attacker controlling the Ceph cluster can deterministically issue a larger rotated ticket to force ceph_buffer realloc in ceph_x_update_authorizer, then trigger an msgr1 OSD/MDS/MON reconnect; no victim-specific memory layout or uncontrollable race is required.
- PR:NPrivileges required, none
- Exploitation requires no privileges on the victim host; any kernel Ceph/RBD/CephFS client already connected to an attacker-controlled or compromised cluster is sufficient, matching other libceph client CVEs where the remote peer drives the bug.
- UI:NUser interaction, none
- After initial Ceph client setup, service-ticket rotation and messenger reconnects occur automatically; no further interactive user action is needed to reach the stale-buffer send path.
- S:UScope, unchanged
- The slab UAF corrupts kernel heap memory on the Ceph client host for local privilege escalation or crash, but does not cross VM, IOMMU, or container sandbox boundaries to another security authority.
- C:HConfidentiality impact, high
- KASAN-confirmed slab use-after-free in _copy_from_iter during authorizer transmission reads freed kmalloc memory, which can disclose adjacent kernel pointers and is classed as exploitable arbitrary read per kernel UAF guidance.
- I:HIntegrity impact, high
- Freed authorizer buffers can be reclaimed with attacker-controlled data before reconnect, enabling heap corruption and control-flow hijack during the stale-pointer copy, consistent with kernel UAF write primitive scoring.
- A:HAvailability impact, high
- The reported KASAN slab-use-after-free in tcp_sendmsg while copying the authorizer reliably causes kernel oops or panic on Ceph client reconnect, and remains repeatable whenever tickets are rotated and msgr1 reconnects.