VulnerabilityPublished 18 Oct 2026

CVE-2026-98449: Linux kernel · smb: client: delete compound mids on send failure before unlock

Affects Linux kernelSource CVE Database V5

Not known to be exploited · fixed in 70783946f3b5d0c06ec7df0f5e7bec2bfad24efb : update Linux kernel when convenient.

Data as of 26 Oct 2026, 14:05 UTC

Severity

Low

Rated Low by Threat Radar's AI analysis · CVSS not yet scored by NVD

EPSS: 0.1% chance of exploitation in 30 days – higher than 5% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 70783946f3b5d0c06ec7df0f5e7bec2bfad24efb, 8f6f8a48399f82f4a83f7b9f25b9707e0062a4f9, 4.21

Exploitation evidence

Disclosed: evidence found.
CVE published 18 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: 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 26 Oct 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.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, 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 70783946f3b5d0c06ec7df0f5e7bec2bfad24efb, 8f6f8a48399f82f4a83f7b9f25b9707e0062a4f9 or 4.21.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected >=4.20.11 <4.21	Fixed in 70783946f3b5d0c06ec7df0f5e7bec2bfad24efb 8f6f8a48399f82f4a83f7b9f25b9707e0062a4f9 4.21
LinuxLinux	Affected =5.0	Fixed in–

AI-suggested

A fix is available in Linux kernel version 4.21 and later. Users should upgrade to version 4.21 or apply the corresponding patches to resolve this issue. No additional mitigation steps are indicated.

Description

A vulnerability in the Linux kernel's SMB client handling causes improper management of compound message IDs (mids) on send failure. Specifically, when sending a compound request fails, the mids remain on the pending queue and are not properly deleted before unlocking the server, leading to double decrement of in-flight credits and kernel warnings. This issue was observed during SMB2 negotiation when socket send fails and has been fixed in Linux kernel version 4.21.

Impact

The vulnerability leads to incorrect credit accounting in the SMB client implementation of the Linux kernel, causing kernel warnings and potential instability during SMB2 negotiation when socket send operations fail. There is no indication of remote code execution or privilege escalation. No known exploits in the wild have been reported.

Summary

The Linux kernel SMB client had a flaw where, upon failure to send a compound request, the compound mids were not deleted from the pending_mid_q before unlocking the server. This caused cifs_abort_connection() to invoke callbacks that returned credits and decremented in_flight counters, followed by compound_send_recv() returning the same credits again, resulting in double decrement and WARNs from smb2_add_credits(). The fix involved deleting the mids on send failure before unlocking and marking them as cancelled to prevent double deletion.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 26 Oct 2026, 11:18 UTC

Technical details

References

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