VulnerabilityPublished 27 May 2026Updated 6 Nov 2026

CVE-2026-45983: Linux kernel · nfsd: never defer requests during idmap lookup

Affects Linux kernelSource CVE Database V5

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Not known to be exploited · fixed in f9c206cdc4266caad6a9a7f46341420a10f03ccb : update Linux kernel when convenient.

Data as of 6 Nov 2026, 16:34 UTC

Severity

Unrated

Rated by Threat Radar · No CVSS score from NVD or the CNA

Thin evidence

One scorer or none

Exploitation: No evidence of active exploitation and no public proof of concept
Automatable: Attackers cannot reliably automate steps 1–4 of the kill chain
Technical impact: Limited control over the software or limited information exposure

CISA SSVC assessment, 2026-11-06.

Patch

Available – fixed in f9c206cdc4266caad6a9a7f46341420a10f03ccb, d75ec4504a4340b033b15cad0303988b3089dd93, b9abb760db20504240a7147f27934d900cd80b23 +5

Exploitation evidence

Disclosed: evidence found.
CVE published 27 May 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 6 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 2f425878b6a71571341dcd3f9e9d1a6f6355da9c, < f9c206cdc4266caad6a9a7f46341420a10f03ccb	Fixed in f9c206cdc4266caad6a9a7f46341420a10f03ccb
LinuxLinux	Affected ≥ 2f425878b6a71571341dcd3f9e9d1a6f6355da9c, < d75ec4504a4340b033b15cad0303988b3089dd93	Fixed in d75ec4504a4340b033b15cad0303988b3089dd93
LinuxLinux	Affected ≥ 2f425878b6a71571341dcd3f9e9d1a6f6355da9c, < b9abb760db20504240a7147f27934d900cd80b23	Fixed in b9abb760db20504240a7147f27934d900cd80b23
LinuxLinux	Affected ≥ 2f425878b6a71571341dcd3f9e9d1a6f6355da9c, < 243f71ed873ff3feeb6f9b5cb145d63f7188b4c4	Fixed in 243f71ed873ff3feeb6f9b5cb145d63f7188b4c4
LinuxLinux	Affected ≥ 2f425878b6a71571341dcd3f9e9d1a6f6355da9c, < 99e17b20fddac19a228d213e00f6b9e1c10daff9	Fixed in 99e17b20fddac19a228d213e00f6b9e1c10daff9
LinuxLinux	Affected ≥ 2f425878b6a71571341dcd3f9e9d1a6f6355da9c, < 063a6f22478ef929625000a2caf54667725c1dfd	Fixed in 063a6f22478ef929625000a2caf54667725c1dfd

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.

References

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