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CVE-2026-52956
libceph: Fix potential out-of-bounds access in __ceph_x_decrypt()
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-2026-52956 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 | vulnerable | 6.1.190-1 | No fix published anywhere yet, neither in Debian nor upstream for the series bookworm tracks. Watch the Debian tracker page for this CVE. Advisories for bookworm have historically landed a median of 23 days after publication. |
| Debian 13trixie | vulnerable | 6.12.113-1 | No fix published anywhere yet, neither in Debian nor upstream for the series trixie tracks. Watch the Debian tracker page for this CVE. Advisories for trixie have historically landed a median of 11 days after publication. |
| 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
In __ceph_x_decrypt(), a part of the buffer p is interpreted as a ceph_x_encrypt_header, and the magic field of this struct is accessed. This happens without any guarantee that the buffer is large enough to hold this struct. The function parameter ciphertext_len represents the length of the ciphertext to decrypt and is guaranteed to be at most the remaining size of the allocated buffer p. However, this value is not necessarily greater than sizeof(ceph_x_encrypt_header). E.g., a message frame of type FRAME_TAG_AUTH_REPLY_MORE, that is just as long to hold the ciphertext at its end with a ciphertext_len of 8 or less, can trigger an out-of-bounds memory access when accessing hdr->magic. This patch fixes the issue by adding a check to ensure that the decrypted plaintext in the buffer is large enough to represent at least the ceph_x_encrypt_header.
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, 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
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
- 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 |
|---|---|---|
| 4.10 | 6.18.57 | 5df268406ef3 |
| 4.10 | 7.0.10 | c7e9b53aebe4 |
| 4.10 | 7.1 | 821365487aa5 |
| 4.9.6 | 0 | 0 |
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 CephX decrypt path processes auth payloads received over the Ceph messenger TCP protocol from monitors/OSDs/MDSs. A malicious or compromised remote Ceph peer can supply the malformed auth frame during connection authentication.
- AC:LAttack complexity, low
- The attacker controls the frame and ciphertext length needed to reach the missing plaintext-size check. No race or unusual victim state is required once the kernel client connects to the attacker-controlled peer.
- PR:NPrivileges required, none
- The vulnerable parsing occurs in the authentication handshake before the remote peer has been authenticated by the kernel client. The attacker needs no privileges on the vulnerable system.
- UI:NUser interaction, none
- In a reasonable deployment, a configured kernel Ceph client connects or reconnects to its Ceph peers automatically. Exploitation does not require an interactive victim action at trigger time.
- S:UScope, unchanged
- The impact is within the kernel/client system processing the Ceph protocol. It does not cross a separate security authority such as a guest-to-host or IOMMU boundary.
- C:NConfidentiality impact, none
- The bug is a bounded out-of-bounds read of the CephX encryption header magic field, but the read value is only compared internally and is not returned to the attacker. There is no practical information disclosure primitive.
- I:NIntegrity impact, none
- The vulnerable code performs no write based on the out-of-bounds access. The fix adds a read-side length check and there is no memory corruption or data modification path.
- A:HAvailability impact, high
- The peer-controlled short plaintext can trigger an out-of-bounds kernel memory access in the auth receive path. Such kernel OOB accesses can produce an oops/panic or otherwise terminate the Ceph client connection, so availability impact is high.