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CVE Record

CVE-2026-31433: ksmbd: fix potencial OOB in get_file_all_info() for compound requests

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix potencial OOB in get_file_all_info() for compound requests When a compound request consists of QUERY_DIRECTORY + QUERY_INFO (FILE_ALL_INFORMATION) and the first command consumes nearly the entire max_trans_size, get_file_all_info() would blindly call smbConvertToUTF16() with PATH_MAX, causing out-of-bounds write beyond the response buffer. In get_file_all_info(), there was a missing validation check for the client-provided OutputBufferLength before copying the filename into FileName field of the smb2_file_all_info structure. If the filename length exceeds the available buffer space, it could lead to potential buffer overflows or memory corruption during smbConvertToUTF16 conversion. This calculating the actual free buffer size using smb2_calc_max_out_buf_len() and returning -EINVAL if the buffer is insufficient and updating smbConvertToUTF16 to use the actual filename length (clamped by PATH_MAX) to ensure a safe copy operation.

HighCVSS 8.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A flaw in the Linux kernel’s ksmbd SMB server can let an authenticated network client overwrite memory when requesting specially arranged file information. A successful trigger could crash the server or potentially compromise confidentiality and integrity. Risk is concentrated on systems running ksmbd and allowing untrusted authenticated SMB access.

Executive priority

Prioritize affected internet-facing or broadly reachable ksmbd servers, especially those serving many or weakly governed accounts. Patch promptly through supported distribution channels. Lower urgency is reasonable only after confirming ksmbd is absent, disabled, or inaccessible to untrusted authenticated clients.

Technical view

A compound SMB2 QUERY_DIRECTORY plus QUERY_INFO request can leave insufficient response-buffer space. get_file_all_info() failed to validate the client-supplied OutputBufferLength before smbConvertToUTF16() copied a filename, permitting an out-of-bounds write. The correction calculates available output space, rejects insufficient buffers, and limits conversion to the actual filename length, capped by PATH_MAX.

Likely exposure

Likely exposure requires Linux systems using ksmbd, reachable over the network by an authenticated low-privilege SMB client. Systems not running ksmbd are not implicated by the supplied evidence. Exact exposure must be determined using vendor kernel packages because backports may make version numbers alone unreliable.

Exploitation context

CVSS 3.1 is 8.8: network reachable, low complexity, low privileges, no user interaction, with potentially high confidentiality, integrity, and availability impact. The bundle marks KEV false and provides no evidence of active exploitation or a public exploit. Treat exploitation status as unconfirmed.

Researcher notes

The vulnerable path depends on response-buffer exhaustion within a compound request and inadequate OutputBufferLength validation. The supplied affected-version data is difficult to interpret and includes commit identifiers and duplicated entries, so avoid conclusions from version strings alone. Confirm distribution backports or stable-commit ancestry. Memory corruption impact is plausible, but reliable code execution is not established by these sources.

Mitigation direction

  • Apply the vendor-supported kernel update containing the referenced ksmbd correction.
  • Check distribution security guidance for package-specific fixed versions and backports.
  • Restrict SMB access to trusted networks and authenticated users until patched.
  • Disable ksmbd where it is unnecessary, following vendor operational guidance.

Validation and detection

  • Confirm whether ksmbd is installed, loaded, enabled, or providing SMB shares.
  • Identify the running kernel package, build, and distribution patch level.
  • Verify the vendor changelog includes CVE-2026-31433 or the referenced correction.
  • Review network controls for untrusted access to the ksmbd service.
  • After updating, confirm the patched kernel is running and SMB functions normally.
Prepared
Confidence
medium
Sources
9

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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CVE-2026-31433 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
8.8 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
3Timeline events
0ADP providers
8Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
8.8CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H2.85.9Linux

Vulnerability scoring details

Base CVSS 3.1 score

8.8High
CVSS 3.1 vector shape for CVE-2026-31433Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxf2283680a80571ca82d710bc6ecd8f8beac67d63, 9f297df20d93411c0b4ddad7f88ba04a7cd36e77, e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d, e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d, e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d, e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d, e2b76ab8b5c9327ab2dae6da05d0752eb2f4771d, 5.15.145, 6.1.71unaffected
LinuxLinux6.6, 0, 5.15.203, 6.1.168, 6.6.131, 6.12.80, 6.18.21, 6.19.11, 7.0affected
Weakness

CWE details

No CWE listed

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