---
id: CVE-2026-99083
title: 'ksmbd: fix heap out-of-bounds write in krb5_authenticate()'
summary: |-
  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 incomi…
severity: high
cvss: 8.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8 <
    59c6dcc5dd9dafe764ca0d40525933b2be69b059
  - >-
    Linux >= 98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8 <
    80af1bde97d5a85ad6f2c40ca894ccc8fa75a27a
  - >-
    Linux >= 98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8 <
    517404e157395d0f8da125ca956c566895dfcd06
  - >-
    Linux >= 98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8 <
    4722d06b2907585074252061b1024a696c1cfc23
  - >-
    Linux >= 98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8 <
    23a0be6a84a38ac169eeab49017934e8e27c65f0
  - Linux 676392184785ace61e939831e7ca44a03d438c3b
  - Linux ef572ffa8eb44111eed2925fbb2adca78bdcbf61
  - Linux 2ba03cecb12ac7ac9e0170e251543c56832d9959
  - Linux >= 5.15.145 < 5.16
  - Linux >= 6.1.40 < 6.2
  - Linux >= 6.4.5 < 6.5
  - Linux 6.5
published: '2026-10-23'
updated: '2026-10-26'
sourceUpdated: '2026-10-26T06:56:58.783Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-99083'
references:
  - url: 'https://git.kernel.org/stable/c/59c6dcc5dd9dafe764ca0d40525933b2be69b059'
  - url: 'https://git.kernel.org/stable/c/80af1bde97d5a85ad6f2c40ca894ccc8fa75a27a'
  - url: 'https://git.kernel.org/stable/c/517404e157395d0f8da125ca956c566895dfcd06'
  - url: 'https://git.kernel.org/stable/c/4722d06b2907585074252061b1024a696c1cfc23'
  - url: 'https://git.kernel.org/stable/c/23a0be6a84a38ac169eeab49017934e8e27c65f0'
tags:
  - cve.org
epss: 0.00408
epssPercentile: 0.34885
ingestedAt: '2026-10-23T13:24:55.512Z'
---

## Overview

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

- `Linux >= 98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8 < 59c6dcc5dd9dafe764ca0d40525933b2be69b059`
- `Linux >= 98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8 < 80af1bde97d5a85ad6f2c40ca894ccc8fa75a27a`
- `Linux >= 98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8 < 517404e157395d0f8da125ca956c566895dfcd06`
- `Linux >= 98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8 < 4722d06b2907585074252061b1024a696c1cfc23`
- `Linux >= 98422bdd4cb3ca4d08844046f6507d7ec2c2b8d8 < 23a0be6a84a38ac169eeab49017934e8e27c65f0`
- `Linux 676392184785ace61e939831e7ca44a03d438c3b`
- `Linux ef572ffa8eb44111eed2925fbb2adca78bdcbf61`
- `Linux 2ba03cecb12ac7ac9e0170e251543c56832d9959`
- `Linux >= 5.15.145 < 5.16`
- `Linux >= 6.1.40 < 6.2`
- `Linux >= 6.4.5 < 6.5`
- `Linux 6.5`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.