Linux Kernel up to 7.1.5/7.2-rc4 ksmbd init_smb2_rsp_hdr allocation of resources

Summaryinfo

A vulnerability labeled as problematic has been found in Linux Kernel up to 7.1.5/7.2-rc4. Impacted is the function init_smb2_rsp_hdr of the component ksmbd. Executing a manipulation can lead to allocation of resources. This vulnerability appears as CVE-2026-68431. The attack may be performed from remote. There is no available exploit.

Detailsinfo

A vulnerability was found in Linux Kernel up to 7.1.5/7.2-rc4. It has been declared as problematic. This vulnerability affects the function init_smb2_rsp_hdr of the component ksmbd. The manipulation with an unknown input leads to a allocation of resources vulnerability. The CWE definition for the vulnerability is CWE-770. The product allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor. As an impact it is known to affect confidentiality. CVE summarizes:

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.

The advisory is shared for download at git.kernel.org. This vulnerability was named CVE-2026-68431 since 07/30/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 08/12/2026). The MITRE ATT&CK project declares the attack technique as T1499.

Upgrading to version 7.1.6 or 7.2-rc5 eliminates this vulnerability. Applying the patch b62c510f59803f82f9b4c76ead2a56833b2984c7/cfc0b8e5080aec87700774e8568765eaa4b7b92b is able to eliminate this problem.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 7.1.0
• 7.1.1
• 7.1.2
• 7.1.3
• 7.1.4
• 7.1.5
• 7.2-rc1
• 7.2-rc2
• 7.2-rc3
• 7.2-rc4

License

• open-source

Website

• Vendor: https://www.kernel.org/

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