CVE-2026-99083ksmbd: fix heap out-of-bounds write in krb5_authenticate()

Official description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix heap out-of-bounds write in krb5_authenticate() In krb5_authenticate(), out_len is calculated to determine available headroom in response_buf for the incoming Kerberos AP-REP token. However, when SMB2_SESSION_SETUP is processed as a non-first element of a compounded SMB2 request, the calculation omits work->next_smb2_rsp_hdr_off. This causes out_len to overstate remaining buffer headroom by the cumulative size of prior responses in the compound chain. Consequently, the length check in ksmbd_krb5_authenticate() (*out_len <= resp->spnego_blob_len) passes erroneously, allowing memcpy() to write the AP-REP blob past the end of response_buf into adjacent kernel heap memory. Fix this by subtracting work->next_smb2_rsp_hdr_off when computing out_len, ensuring it accurately reflects physical remaining buffer space.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/a07dfb33112a42437f9d2d0bfd35c68575257381
• https://git.kernel.org/stable/c/1f73a6d40f4d1bae4f3491c0ec1ea8ee6ce035ff
• https://git.kernel.org/stable/c/59c6dcc5dd9dafe764ca0d40525933b2be69b059
• https://git.kernel.org/stable/c/80af1bde97d5a85ad6f2c40ca894ccc8fa75a27a
• https://git.kernel.org/stable/c/517404e157395d0f8da125ca956c566895dfcd06
• https://git.kernel.org/stable/c/4722d06b2907585074252061b1024a696c1cfc23
• https://git.kernel.org/stable/c/23a0be6a84a38ac169eeab49017934e8e27c65f0