---
id: CVE-2026-23397
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  nfnetlink_osf: validate individual option lengths in fingerprints

  nfnl_osf_add_callback() validates opt_num bounds and string
  NUL-termination but does not check indivi…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  nfnetlink_osf: validate individual option lengths in fingerprints

  nfnl_osf_add_callback() validates opt_num bounds and string
  NUL-termination but does not check indivi…
severity: high
cvss: 7.1
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H'
cwe:
  - CWE-125
vendor: linux
product: linux_kernel
affected:
  - 'linux_kernel >= 2.6.31.1, < 5.10.253'
  - 'linux_kernel >= 5.11, < 5.15.203'
  - 'linux_kernel >= 5.16, < 6.1.167'
  - 'linux_kernel >= 6.2, < 6.6.130'
  - 'linux_kernel >= 6.7, < 6.12.78'
  - 'linux_kernel >= 6.13, < 6.18.20'
  - 'linux_kernel >= 6.19, < 6.19.10'
  - linux_kernel = 2.6.31
  - linux_kernel = 7.0
patched:
  - linux_kernel 6.19.10
published: '2026-03-26'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T02:18:54.960'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-23397'
references:
  - url: 'https://git.kernel.org/stable/c/224f4678812e1a7bc8341bcb666773a0aec5ea6f'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/3932620c04c2938c93c0890c225960d3d34ba355'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/3c11b5c2436a3a5b450612ab160e3a525b28cfb5'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/4c6aa008b913e808c4f4d3cde36cb1d9bb5967c6'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/aa0574182c46963c3cdb8cde46ec93aca21100d8'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/dbdfaae9609629a9569362e3b8f33d0a20fd783c'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/e9cf17b91e733fec725ebcc0b3098bc5ccd505e0'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/ec8bf0571b142f29dc0b68ae2ac3952f7a464b38'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-019113.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-082556.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-457936.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
  - url: 'https://cert-portal.siemens.com/productcert/html/ssa-784472.html'
    label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e
tags:
  - nvd
  - cve.org
epss: 0.00127
epssPercentile: 0.02369
ingestedAt: '2026-09-08T15:33:26.992Z'
---

## Overview

In the Linux kernel, the following vulnerability has been resolved:

nfnetlink_osf: validate individual option lengths in fingerprints

nfnl_osf_add_callback() validates opt_num bounds and string
NUL-termination but does not check individual option length fields.
A zero-length option causes nf_osf_match_one() to enter the option
matching loop even when foptsize sums to zero, which matches packets
with no TCP options where ctx->optp is NULL:

 Oops: general protection fault
 KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
 RIP: 0010:nf_osf_match_one (net/netfilter/nfnetlink_osf.c:98)
 Call Trace:
  nf_osf_match (net/netfilter/nfnetlink_osf.c:227)
  xt_osf_match_packet (net/netfilter/xt_osf.c:32)
  ipt_do_table (net/ipv4/netfilter/ip_tables.c:293)
  nf_hook_slow (net/netfilter/core.c:623)
  ip_local_deliver (net/ipv4/ip_input.c:262)
  ip_rcv (net/ipv4/ip_input.c:573)

Additionally, an MSS option (kind=2) with length < 4 causes
out-of-bounds reads when nf_osf_match_one() unconditionally accesses
optp[2] and optp[3] for MSS value extraction.  While RFC 9293
section 3.2 specifies that the MSS option is always exactly 4
bytes (Kind=2, Length=4), the check uses "< 4" rather than
"!= 4" because lengths greater than 4 do not cause memory
safety issues -- the buffer is guaranteed to be at least
foptsize bytes by the ctx->optsize == foptsize check.

Reject fingerprints where any option has zero length, or where an MSS
option has length less than 4, at add time rather than trusting these
values in the packet matching hot path.

## Affected

- `linux_kernel >= 2.6.31.1, < 5.10.253`
- `linux_kernel >= 5.11, < 5.15.203`
- `linux_kernel >= 5.16, < 6.1.167`
- `linux_kernel >= 6.2, < 6.6.130`
- `linux_kernel >= 6.7, < 6.12.78`
- `linux_kernel >= 6.13, < 6.18.20`
- `linux_kernel >= 6.19, < 6.19.10`
- `linux_kernel = 2.6.31`
- `linux_kernel = 7.0`

## Remediation

Upgrade past the affected range:

- `linux_kernel 6.19.10`