Linux Kernel: security vulnerability (CVE-2026-99275)

What is affected, what to do

In the Linux kernel, the following vulnerability has been resolved: smb: client: reject short SESSION_SETUP responses smb2_check_message() accepts frames shorter than struct smb2_pdu when the SMB2 status is non-zero, before the minimum-PDU check added by b4694f269e66d. A 64-byte STATUS_MORE_PROCESSING_REQUIRED SESSION_SETUP response is therefore accepted even though it cannot contain the SecurityBufferOffset and SecurityBufferLength fields.

Update Linux Kernel to version 7.3.2, Linux Kernel to version 7.4-rc1.

Affected

• Linux Kernel lt 3.6..7.3.2
• Linux Kernel lt 7.4..7.4-rc1

Fixed in

• Linux Kernel 7.3.2
• Linux Kernel 7.4-rc1

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Metrics

Detection rules

No NEOSEC detection rule is available for this vulnerability yet.

Classification under NIS2 and CRA

Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

NIS2

NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

Read in glossary

Handle the vulnerability in regular vulnerability handling under Art. 21(2)(e) NIS2.

CRA

The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

Read in glossary

From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.

ISO/IEC 27001

ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

Read in glossary

Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

Description

In the Linux kernel, the following vulnerability has been resolved: smb: client: reject short SESSION_SETUP responses smb2_check_message() accepts frames shorter than struct smb2_pdu when the SMB2 status is non-zero, before the minimum-PDU check added by b4694f269e66d. A 64-byte STATUS_MORE_PROCESSING_REQUIRED SESSION_SETUP response is therefore accepted even though it cannot contain the SecurityBufferOffset and SecurityBufferLength fields. The parser then reads those fields from stale bytes left in the reused receive buffer by an earlier frame. With a long stale SecurityBufferLength, decode_ntlmssp_challenge() copies up to about 64 KB from beyond the receive object and sends the data back to the server in the NTLMv2 AUTHENTICATE target info. Reject short MPR SESSION_SETUP responses before the short-error path, and validate SecurityBufferOffset + SecurityBufferLength against the received response length before decoding the challenge. The ordering bypass is not new: the short-error early return predates b4694f269e66d, and the unvalidated SecurityBufferLength read predates the 2016 raw NTLMSSP split in 166cea4dc3a4, so all supported stable trees are affected. Reproduced on 6.6.87.2; the path is unchanged on mainline.

Source: cvelistv5, NVD (NIST)

Vendors and products

• Linux Linux

References & sources

• git.kernel.orgstable/c/4d8930afa3446041358a7db33e7b23a0bb9459b5
• git.kernel.orgstable/c/df63e01933886153e40706483b9635b2456ad91f

Changes to this CVE

Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

1. 07.11.2026ReceivedLinux

   Description added or changed

   New references:

   • https://git.kernel.org/stable/c/4d8930afa3446041358a7db33e7b23a0bb9459b5
   • https://git.kernel.org/stable/c/df63e01933886153e40706483b9635b2456ad91f
   Show 4 original changes

   Individual changes of this event as published by NVD

   Type	Action	Before	After
   Description	added	—	In the Linux kernel, the following vulnerability has been resolved: smb: client: reject short SESSION_SETUP responses smb2_check_message() accepts frames shorter than struct smb2_pdu when the SMB2 status is non-zero, before the minimum-PDU check added by b4694f269e66d. A 64-byte STATUS_MORE_PROCESSING_REQUIRED SESSION_SETUP response is therefore accepted even though it cannot contain the SecurityBufferOffset and SecurityBufferLength fields. The parser then reads those fields from stale bytes left in the reused receive buffer by an earlier frame. With a long stale SecurityBufferLength, decode_ntlmssp_challenge() copies up to about 64 KB from beyond the receive object and sends the data back to the server in the NTLMv2 AUTHENTICATE target info. Reject short MPR SESSION_SETUP responses before the short-error path, and validate SecurityBufferOffset + SecurityBufferLength against the received response length before decoding the challenge. The ordering bypass is not new: the short-error early return predates b4694f269e66d, and the unvalidated SecurityBufferLength read predates the 2016 raw NTLMSSP split in 166cea4dc3a4, so all supported stable trees are affected. Reproduced on 6.6.87.2; the path is unchanged on mainline.
   Affected versions (publisher)	added	—	New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/99xxx/CVE-2026-99275.json">CVE-2026-99275</a>
   Reference	added	—	https://git.kernel.org/stable/c/4d8930afa3446041358a7db33e7b23a0bb9459b5
   Reference	added	—	https://git.kernel.org/stable/c/df63e01933886153e40706483b9635b2456ad91f

   Source identifier: 416baaa9-dc9f-4396-8d5f-8c081fb06d67