Linux KernelOperating system · Linux
CVE-2026-52955
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedIn the Linux kernel, the following vulnerability has been resolved: libceph: Fix potential out-of-bounds access in crush_decode() A message of type CEPH_MSG_OSD_MAP containing a crush map with at least one bucket has two fields holding the bucket algorithm. If the values in these two fields differ, an out-of-bounds access can occur. This is the case because the first algorithm field (alg) is used to allocate the correct amount of memory for a bucket of this type, while the second algorithm field inside the bucket (b->alg) is used in the subsequent processing. This patch fixes the issue by adding a check that compares alg and b->alg and aborts the processing in case they differ. Furthermore, b->alg is set to 0 in this case, because the destruction of the crush map also uses this field to determine the bucket type, which can again result in an out-of-bounds access when trying to free the memory pointed to by the fields of the bucket. To correctly free the memory allocated for the bucket in such a case, the corresponding call to kfree is moved from the algorithm-specific crush_destroy_bucket functions to the generic crush_destroy_bucket().
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceOut-of-bounds access vulnerability in Linux kernel's libceph crush_decode() function. When processing CEPH_MSG_OSD_MAP messages containing a crush map, if two algorithm fields (alg used for memory allocation vs b->alg used for processing) differ, memory corruption occurs. The fix adds validation comparing these fields and moves memory freeing to the generic destruction function.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
Linux KernelOperating system
>= 2.6.34.1, < 5.10.258>= 5.11, < 5.15.209>= 5.16, < 6.1.175>= 6.2, < 6.6.141>= 6.7, < 6.12.91>= 6.13, < 6.18.33>= 6.19, < 7.0.10= 2.6.34= 7.1CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Determine if Ceph is deployedRun commands such as 'ceph status', 'ceph -s', or check for running ceph processes with 'ps aux | grep ceph'Affected if Ceph is not deployed - the vulnerability only affects systems using libceph for Ceph cluster communication
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Check if libceph kernel module is loadedRun 'lsmod | grep libceph' or check /proc/modules for libceph entriesAffected if The libceph module is not loaded - the vulnerability exists in the kernel's libceph implementation
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Identify the kernel versionRun 'uname -r' or 'cat /proc/version' and compare against the kernel version range that includes the fix for this vulnerabilityAffected if The running kernel version predates the patch that adds alg/b->alg validation in crush_decode()
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Verify OSD daemons are runningRun 'ceph osd stat' or 'systemctl status ceph-osd' (or check process list) to confirm OSD services that process CEPH_MSG_OSD_MAP messages are activeAffected if No OSD daemons are running - the vulnerable code path through crush_decode() is only triggered when processing OSD map messages
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Check for crash logs or kernel errors related to crushReview /var/log/messages, dmesg output, or kernel crash dumps for entries mentioning 'crush_decode', 'crush_map', or OSD map processing errorsAffected if Recent crash logs show out-of-bounds access errors in crush map handling, indicating potential exploitation or triggering of the vulnerable code path
A system is affected if it runs a Linux kernel with libceph, has Ceph OSD services deployed, and runs a kernel version that predates the patch adding alg/b->alg field validation in crush_decode().
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped5.10.2585.15.2096.1.175
Update the Linux kernel to the version containing the patch. The fix validates algorithm field consistency and properly manages bucket memory deallocation.
Upgrade to a Linux kernel version containing the crush_decode() fix. The fix was applied to the Linux kernel mainline. Check kernel release notes for versions containing the libceph crush_decode security fix.
- 1. Apply the kernel patch that adds a check comparing alg and b->alg in the crush_decode() function in libceph
- 2. Ensure b->alg is set to 0 when alg and b->alg differ to prevent out-of-bounds access during crush map destruction
- 3. Move the kfree() call from algorithm-specific crush_destroy_bucket functions to the generic crush_destroy_bucket() to correctly free memory when algorithms mismatch
- 4. Rebuild the kernel with the patched libceph code
- 5. Reboot the system with the patched kernel
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Linux Kernel
Scoped from the published advisory
- Consultation3.0 h
- Implementation6.0 h
- Testing5.0 h
- Review / QA3.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,752.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-52955 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-52955 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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