VulnerabilityPublished 24 Apr 2026Updated 5 Nov 2026

CVE-2026-31535: Linux kernel · smb: client: make use of smbdirect_socket.recv_io.credits.available

Affects Linux kernelSource CVE Database V5

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Not known to be exploited · fixed in f664e6e8a81103cb45c8802a9bc7499e0902c458 : update Linux kernel when convenient.

Data as of 5 Nov 2026, 22:06 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, 2026-11-05.

Patch

Available – fixed in f664e6e8a81103cb45c8802a9bc7499e0902c458, be8845ad5d6558703d20567d8702155598325db8, 9911b1ed187a770a43950bf51f340ad4b7beecba

Exploitation evidence

Disclosed: evidence found.
CVE published 24 Apr 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 5 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 Linux kernel to f664e6e8a81103cb45c8802a9bc7499e0902c458, be8845ad5d6558703d20567d8702155598325db8 or 9911b1ed187a770a43950bf51f340ad4b7beecba.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 5fb9b459b3686e366640edd4e62805ef7b4de927, < f664e6e8a81103cb45c8802a9bc7499e0902c458	Fixed in f664e6e8a81103cb45c8802a9bc7499e0902c458
LinuxLinux	Affected ≥ 5fb9b459b3686e366640edd4e62805ef7b4de927, < be8845ad5d6558703d20567d8702155598325db8	Fixed in be8845ad5d6558703d20567d8702155598325db8
LinuxLinux	Affected ≥ 5fb9b459b3686e366640edd4e62805ef7b4de927, < 9911b1ed187a770a43950bf51f340ad4b7beecba	Fixed in 9911b1ed187a770a43950bf51f340ad4b7beecba
LinuxLinux	Affected =6.18	Fixed in–

AI-suggested

The vulnerability has been fixed in the Linux kernel. Users should update to the fixed versions identified by the commits f664e6e8a81103cb45c8802a9bc7499e0902c458, be8845ad5d6558703d20567d8702155598325db8, and 9911b1ed187a770a43950bf51f340ad4b7beecba. No additional mitigation steps are indicated.

Description

A race condition in the Linux kernel SMB client handling of recv credits was identified and resolved. The vulnerability involved incorrect management of receive credits due to a timing window between hardware receipt and processing completion, potentially granting credits that do not exist. The fix introduced a dedicated counter for available credits to accurately track and manage them.

Impact

The vulnerability could lead to incorrect credit management in SMB Direct communication within the Linux kernel, potentially causing protocol inconsistencies or communication errors. The input does not specify direct exploitation impact such as privilege escalation or denial of service, nor does it confirm exploitation in the wild.

Summary

CVE-2026-31535 addresses a race condition in the Linux kernel's SMB client implementation related to the management of receive credits. The original logic counted posted recv_io and granted credits, but this approach was racy because the peer might have already consumed a credit before the kernel processed the completion, creating a window where credits could be incorrectly granted. The vulnerability was resolved by implementing a dedicated counter for available credits, which increments when new receive buffers are posted and decrements when credits are granted to the peer. This fix prevents the kernel from granting non-existent credits and ensures proper credit accounting in SMB Direct communication.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 5 Nov 2026, 22:06 UTC

Technical details

References

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