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CVE-2026-31478VulnerabilityPublished Updated

smb2_calc_max_out_buf_len() · ksmbd: replace hardcoded hdr2_len with offsetof()

Affects MicrosoftSource GCVE Database

0
Authoritative record:CVE-2026-31478· Critical 9.8

Not known to be exploited · CVSS 9.8 Critical · fixed in c3a89e3ec1ccf64fa6a34e391e1581ebbcba8683 : patch Microsoft as a priority.

Data as of 27 Oct 2026, 00:35 UTC

CVSS 3.1 base score
9.8Critical
How severe the flaw is on the 0–10 CVSS scale.
Patch
Available – fixed in c3a89e3ec1ccf64fa6a34e391e1581ebbcba8683, 80824c7e527b70cf9039534e60aff592e8f209d1, 70b4c414889492c522b6e4331562360f49be2361 +6
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 22 Apr 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq 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.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
LinuxLinuxAffected
  • >=5.15.145 <5.15.203
  • >=6.1.71 <6.1.168
Fixed in
  • c3a89e3ec1ccf64fa6a34e391e1581ebbcba8683
  • 80824c7e527b70cf9039534e60aff592e8f209d1
  • 70b4c414889492c522b6e4331562360f49be2361
  • 9a7166f0ef8cbb7bb48dd05e2471d995566003f5
  • 6aef1765d6807e0f027cd87f6ac973eb0879a46d
  • 6.1.168
  • 5.15.203
  • 4cb537ae4f37d7d0f617815ed4bed7173fb50861
  • 0e55f63dd08f09651d39e1b709a91705a8a0ddcb
LinuxLinuxAffected
  • =6.6
Fixed in–

AI-suggested

Since the vulnerability is published and the description mentions a code change, it is likely that a fix exists or is planned. Users should consult the Microsoft Security Response Center or official advisories for patch availability and remediation instructions.

Description

This vulnerability involves the ksmbd component where a hardcoded header length value (hdr2_len) is replaced with a safer calculation using offsetof() in the smb2_calc_max_out_buf_len() function. The fix addresses a coding practice issue in Microsoft software versions 2.0 and 3.0. No CVSS score or detailed impact information is provided.

References

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