# CVE-2026-52956: libceph: Fix potential out-of-bounds access in __ceph_x_decrypt()

> An out-of-bounds access in the Linux kernel's Ceph filesystem allows attackers to cause denial of service or potentially execute code via crafted messages.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 24 Jun 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-90276, BELL-CVE-2026-52956, DEBIAN-CVE-2026-52956, GHSA-wvxf-4p9h-5vg9, ROOT-OS-DEBIAN-11-CVE-2026-52956, ROOT-OS-DEBIAN-12-CVE-2026-52956, ROOT-OS-DEBIAN-13-CVE-2026-52956, ROOT-OS-UBUNTU-2204-CVE-2026-52956, ROOT-OS-UBUNTU-2404-CVE-2026-52956, UBUNTU-CVE-2026-52956

## What is CVE-2026-52956?

CVE-2026-52956 is a high-severity memory corruption vulnerability in Linux kernel, published on 24 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

libceph: Fix potential out-of-bounds access in __ceph_x_decrypt()

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.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-52956?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-52956?

Apply the vendor's patch.

## Is CVE-2026-52956 being exploited?

There is no known exploitation of CVE-2026-52956 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-52956 and fix it if it is affected.

What it is: CVE-2026-52956 is a high-severity memory corruption vulnerability in Linux kernel, published on 24 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-52956 in the wild and no public exploit code.

Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-52956/ (Markdown: https://insights.sbomify.com/CVE-2026-52956/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-52956
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-52956
- OSV: https://osv.dev/vulnerability/CVE-2026-52956

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-52956/
Summaries are generated and may contain mistakes; the official description above is the record.