GHSA-W9RR-8FX7-936W

Vulnerability from github – Published: 2026-04-13 15:31 – Updated: 2026-04-18 09:30
VLAI?
Details

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.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-31427"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-04-13T14:16:12Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nf_conntrack_sip: fix use of uninitialized rtp_addr in process_sdp\n\nprocess_sdp() declares union nf_inet_addr rtp_addr on the stack and\npasses it to the nf_nat_sip sdp_session hook after walking the SDP\nmedia descriptions. However rtp_addr is only initialized inside the\nmedia loop when a recognized media type with a non-zero port is found.\n\nIf the SDP body contains no m= lines, only inactive media sections\n(m=audio 0 ...) or only unrecognized media types, rtp_addr is never\nassigned. Despite that, the function still calls hooks-\u003esdp_session()\nwith \u0026rtp_addr, causing nf_nat_sdp_session() to format the stale stack\nvalue as an IP address and rewrite the SDP session owner and connection\nlines with it.\n\nWith CONFIG_INIT_STACK_ALL_ZERO (default on most distributions) this\nresults in the session-level o= and c= addresses being rewritten to\n0.0.0.0 for inactive SDP sessions. Without stack auto-init the\nrewritten address is whatever happened to be on the stack.\n\nFix this by pre-initializing rtp_addr from the session-level connection\naddress (caddr) when available, and tracking via a have_rtp_addr flag\nwhether any valid address was established. Skip the sdp_session hook\nentirely when no valid address exists.",
  "id": "GHSA-w9rr-8fx7-936w",
  "modified": "2026-04-18T09:30:20Z",
  "published": "2026-04-13T15:31:42Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-31427"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/01f34a80ac23ae90b1909b94b4ed05343a62f646"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/52fdda318ef2362fc5936385bcb8b3d0328ee629"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6a2b724460cb67caed500c508c2ae5cf012e4db4"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6e5e3c87b7e6212f1d8414fc2e4d158b01e12025"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/7edca70751b9bdb5b83eed53cde21eccf3c86147"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/82baeb871e8f04906bc886273fdf0209e1754eb3"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/faa6ea32797a1847790514ff0da1be1d09771580"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/fe463e76c9b4b0b43b5ee8961b4c500231f1a3f6"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}


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