---
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 >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    59c6dcc5dd9dafe764ca0d40525933b2be69b059
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    80af1bde97d5a85ad6f2c40ca894ccc8fa75a27a
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    517404e157395d0f8da125ca956c566895dfcd06
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    4722d06b2907585074252061b1024a696c1cfc23
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    23a0be6a84a38ac169eeab49017934e8e27c65f0
  - Linux < 6.6.160
  - Linux < 6.12.114
  - Linux < 6.18.58
  - Linux < 7.2.12
  - Linux (all versions)
published: '2026-10-23'
updated: '2026-10-24'
sourceUpdated: '2026-10-24T14:10:24.950Z'
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: 0.00209
epssPercentile: 0.10498
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 >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 59c6dcc5dd9dafe764ca0d40525933b2be69b059`
- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 80af1bde97d5a85ad6f2c40ca894ccc8fa75a27a`
- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 517404e157395d0f8da125ca956c566895dfcd06`
- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 4722d06b2907585074252061b1024a696c1cfc23`
- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 23a0be6a84a38ac169eeab49017934e8e27c65f0`
- `Linux < 6.6.160`
- `Linux < 6.12.114`
- `Linux < 6.18.58`
- `Linux < 7.2.12`
- `Linux (all versions)`

## Remediation

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