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NVD / CVE Program· CNA Linux

CVE-2026-68431: ksmbd: validate minimum PDU size for transform requests

Noroxi assessment

Priority: Monitor (action score 36/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.36% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: Linux Linux 22f1aa35b87e471cc31b35b74451f46630863b12, 32e486b70c256d5ef4baa5a2936ade2fea50e8eb, 5.15.217.

Low priority for now. Upgrade to Linux Linux 22f1aa35b87e471cc31b35b74451f46630863b12, 32e486b70c256d5ef4baa5a2936ade2fea50e8eb, 5.15.217 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

In the Linux kernel, the following vulnerability has been resolved: ksmbd: validate minimum PDU size for transform requests The receive path applies the minimum SMB2 PDU size check only when ProtocolId is SMB2_PROTO_NUMBER. A packet carrying SMB2_TRANSFORM_PROTO_NUM bypasses the check even when the negotiated dialect does not provide transform handling. On an SMB 2.1 connection, a short transform packet therefore reaches init_smb2_rsp_hdr(), which interprets the request as a full SMB2 header and reads beyond the request allocation. The copied fields can then be returned to the unauthenticated client. Compression transforms are converted to ordinary SMB2 messages before protocol validation. After that conversion, validate ordinary SMB2 requests against SMB2_MIN_SUPPORTED_PDU_SIZE and require encryption transform requests to contain both a transform header and an SMB2 header. This rejects truncated requests before work allocation.

CriticalCVSS 9.1 · v3.1—No exploit Fix available
Published
Aug 11, 2026
Updated
Aug 23, 2026
EPSS
0.3% · 30th percentile
CWE
—

Report tools

JSON

Action score

36

Monitor

Low priority for now.

CVSS
36 / 40 · 9.1 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.3%

CNA vs NVD score

NVD
—
CNA · Linux
9.1
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

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  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

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When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • e9cb7be2fcbaee9e808b729e92948d38d52e5add, 6.4affected
    • df3a4518aee64f21bcafa891105b468413f27431 and later · before 22f1aa35b87e471cc31b35b74451f46630863b12affected · git
    • 543c12c2644e772caa6880662c2a852cfdc5a10c and later · before 928dda88d0e13fbca381255028f65b244343a4eaaffected · git
    • 368ba06881c395f1c9a7ba22203cf8d78b4addc0 and later · before d8e5c5672724b8f3c4c099d2cf60239c996e5424affected · git
    • 368ba06881c395f1c9a7ba22203cf8d78b4addc0 and later · before 32e486b70c256d5ef4baa5a2936ade2fea50e8ebaffected · git
    • 368ba06881c395f1c9a7ba22203cf8d78b4addc0 and later · before d9e9753dfd43bd27c956578df7804a3c90b80fdcaffected · git
    • 368ba06881c395f1c9a7ba22203cf8d78b4addc0 and later · before b62c510f59803f82f9b4c76ead2a56833b2984c7affected · git
    • 368ba06881c395f1c9a7ba22203cf8d78b4addc0 and later · before cfc0b8e5080aec87700774e8568765eaa4b7b92baffected · git
    • 5.15.145 and later · before 5.15.217affected · semver
    • 6.1.34 and later · before 6.1.184affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.187-16.1.187-1
Debian:12linux-6.12before 6.12.107-1~deb12u16.12.107-1~deb12u1
Debian:13linuxbefore 6.12.105-16.12.105-1
Debian:14linuxbefore 7.1.6-17.1.6-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-74705udp: fix potential use-after-free in tunnel segmentation
    40Plan
  • CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment
    40Plan
  • CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2026-68429Aug 11, 2026 · drm/dp_mst: Handle torn-down topology gracefully in drm_dp_mst_topology_queue_probe()
    0Monitor
  • ← EarlierCVE-2026-68430Aug 11, 2026 · drm/amdgpu/gfx8: drop unecessary BUG_ON()
    0Monitor
  • Later →CVE-2026-68434Aug 11, 2026 · serial: 8250_mid: Fix NULL function pointer dereference on DNV/ICX-D/SNR platforms
    0Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux22f1aa35b87e471cc31b35b74451f46630863b12Vendor (CNA)
Linux Linux32e486b70c256d5ef4baa5a2936ade2fea50e8ebVendor (CNA)
Linux Linux5.15.217Vendor (CNA)
Linux Linux6.1.184Vendor (CNA)
Linux Linux6.4Vendor (CNA)
Linux Linux928dda88d0e13fbca381255028f65b244343a4eaVendor (CNA)
Linux Linuxb62c510f59803f82f9b4c76ead2a56833b2984c7Vendor (CNA)
Linux Linuxcfc0b8e5080aec87700774e8568765eaa4b7b92bVendor (CNA)
Linux Linuxd8e5c5672724b8f3c4c099d2cf60239c996e5424Vendor (CNA)
Linux Linuxd9e9753dfd43bd27c956578df7804a3c90b80fdcVendor (CNA)
debian:linux6.1.187-1 · Debian:12Package registry (OSV)
debian:linux-6.126.12.107-1~deb12u1 · Debian:12Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
None
Availability impact
High

Weakness class (CWE)

—

CVSS vector

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

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (6 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records