{"id":"CVE-2026-31427","state":"PUBLISHED","title":"netfilter: nf_conntrack_sip: fix use of uninitialized rtp_addr in process_sdp","description":"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->sdp_session()\nwith &rtp_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.","publishedAt":"2026-04-13T13:40:30.280Z","updatedAt":"2026-10-15T01:16:08.245Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"4ab9e64e5e3c0516577818804aaf13a630d67bc9","status":"affected","lessThan":"faa6ea32797a1847790514ff0da1be1d09771580","versionType":"git"},{"version":"4ab9e64e5e3c0516577818804aaf13a630d67bc9","status":"affected","lessThan":"82baeb871e8f04906bc886273fdf0209e1754eb3","versionType":"git"},{"version":"4ab9e64e5e3c0516577818804aaf13a630d67bc9","status":"affected","lessThan":"6e5e3c87b7e6212f1d8414fc2e4d158b01e12025","versionType":"git"},{"version":"4ab9e64e5e3c0516577818804aaf13a630d67bc9","status":"affected","lessThan":"fe463e76c9b4b0b43b5ee8961b4c500231f1a3f6","versionType":"git"},{"version":"4ab9e64e5e3c0516577818804aaf13a630d67bc9","status":"affected","lessThan":"7edca70751b9bdb5b83eed53cde21eccf3c86147","versionType":"git"},{"version":"4ab9e64e5e3c0516577818804aaf13a630d67bc9","status":"affected","lessThan":"01f34a80ac23ae90b1909b94b4ed05343a62f646","versionType":"git"},{"version":"4ab9e64e5e3c0516577818804aaf13a630d67bc9","status":"affected","lessThan":"52fdda318ef2362fc5936385bcb8b3d0328ee629","versionType":"git"},{"version":"4ab9e64e5e3c0516577818804aaf13a630d67bc9","status":"affected","lessThan":"6a2b724460cb67caed500c508c2ae5cf012e4db4","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/netfilter/nf_conntrack_sip.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"2.6.26","status":"affected"},{"version":"0","status":"unaffected","lessThan":"2.6.26","versionType":"semver"},{"version":"5.10.253","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.203","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.168","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.131","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.80","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.21","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.11","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/netfilter/nf_conntrack_sip.c"]}],"references":["https://git.kernel.org/stable/c/faa6ea32797a1847790514ff0da1be1d09771580","https://git.kernel.org/stable/c/82baeb871e8f04906bc886273fdf0209e1754eb3","https://git.kernel.org/stable/c/6e5e3c87b7e6212f1d8414fc2e4d158b01e12025","https://git.kernel.org/stable/c/fe463e76c9b4b0b43b5ee8961b4c500231f1a3f6","https://git.kernel.org/stable/c/7edca70751b9bdb5b83eed53cde21eccf3c86147","https://git.kernel.org/stable/c/01f34a80ac23ae90b1909b94b4ed05343a62f646","https://git.kernel.org/stable/c/52fdda318ef2362fc5936385bcb8b3d0328ee629","https://git.kernel.org/stable/c/6a2b724460cb67caed500c508c2ae5cf012e4db4","https://cert-portal.siemens.com/productcert/html/ssa-082556.html","https://cert-portal.siemens.com/productcert/html/ssa-019113.html","https://cert-portal.siemens.com/productcert/html/ssa-457936.html"],"weaknesses":[],"ingestedAt":"2026-10-29T20:11:40.391Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/31xxx/CVE-2026-31427.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-31427","state":"PUBLISHED","datePublished":"2026-04-13T13:40:30.280Z","dateUpdated":"2026-10-15T01:16:08.245Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-03-09T15:48:24.088Z"},"containers":{"cna":{"title":"netfilter: nf_conntrack_sip: fix use of uninitialized rtp_addr in process_sdp","descriptions":[{"lang":"en","value":"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->sdp_session()\nwith &rtp_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. 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