---
id: CVE-2026-31427
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  netfilter: nf_conntrack_sip: fix use of uninitialized rtp_addr in process_sdp

  process_sdp() declares union nf_inet_addr rtp_addr on the stack and
  passes it to the nf_n…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  netfilter: nf_conntrack_sip: fix use of uninitialized rtp_addr in process_sdp

  process_sdp() declares union nf_inet_addr rtp_addr on the stack and
  passes it to the nf_n…
severity: medium
cvss: 5.5
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-908
vendor: linux
product: linux_kernel
affected:
  - 'linux_kernel >= 2.6.26, < 5.10.253'
  - 'linux_kernel >= 5.11, < 5.15.203'
  - 'linux_kernel >= 5.16, < 6.1.168'
  - 'linux_kernel >= 6.2, < 6.6.131'
  - 'linux_kernel >= 6.7, < 6.12.80'
  - 'linux_kernel >= 6.13, < 6.18.21'
  - 'linux_kernel >= 6.19, < 6.19.11'
  - linux_kernel = 7.0
patched:
  - linux_kernel 6.19.11
published: '2026-04-13'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T02:19:04.573'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-31427'
references:
  - url: 'https://git.kernel.org/stable/c/01f34a80ac23ae90b1909b94b4ed05343a62f646'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/52fdda318ef2362fc5936385bcb8b3d0328ee629'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/6a2b724460cb67caed500c508c2ae5cf012e4db4'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/6e5e3c87b7e6212f1d8414fc2e4d158b01e12025'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/7edca70751b9bdb5b83eed53cde21eccf3c86147'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/82baeb871e8f04906bc886273fdf0209e1754eb3'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/faa6ea32797a1847790514ff0da1be1d09771580'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/fe463e76c9b4b0b43b5ee8961b4c500231f1a3f6'
    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
tags:
  - nvd
  - cve.org
epss: 0.0012
epssPercentile: 0.01836
ingestedAt: '2026-09-08T15:33:26.990Z'
---

## Overview

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

netfilter: nf_conntrack_sip: fix use of uninitialized rtp_addr in process_sdp

process_sdp() declares union nf_inet_addr rtp_addr on the stack and
passes it to the nf_nat_sip sdp_session hook after walking the SDP
media descriptions. However rtp_addr is only initialized inside the
media loop when a recognized media type with a non-zero port is found.

If the SDP body contains no m= lines, only inactive media sections
(m=audio 0 ...) or only unrecognized media types, rtp_addr is never
assigned. Despite that, the function still calls hooks->sdp_session()
with &rtp_addr, causing nf_nat_sdp_session() to format the stale stack
value as an IP address and rewrite the SDP session owner and connection
lines with it.

With CONFIG_INIT_STACK_ALL_ZERO (default on most distributions) this
results in the session-level o= and c= addresses being rewritten to
0.0.0.0 for inactive SDP sessions. Without stack auto-init the
rewritten address is whatever happened to be on the stack.

Fix this by pre-initializing rtp_addr from the session-level connection
address (caddr) when available, and tracking via a have_rtp_addr flag
whether any valid address was established. Skip the sdp_session hook
entirely when no valid address exists.

## Affected

- `linux_kernel >= 2.6.26, < 5.10.253`
- `linux_kernel >= 5.11, < 5.15.203`
- `linux_kernel >= 5.16, < 6.1.168`
- `linux_kernel >= 6.2, < 6.6.131`
- `linux_kernel >= 6.7, < 6.12.80`
- `linux_kernel >= 6.13, < 6.18.21`
- `linux_kernel >= 6.19, < 6.19.11`
- `linux_kernel = 7.0`

## Remediation

Upgrade past the affected range:

- `linux_kernel 6.19.11`