{"id":"CVE-2026-23456","state":"PUBLISHED","title":"netfilter: nf_conntrack_h323: fix OOB read in decode_int() CONS case","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nf_conntrack_h323: fix OOB read in decode_int() CONS case\n\nIn decode_int(), the CONS case calls get_bits(bs, 2) to read a length\nvalue, then calls get_uint(bs, len) without checking that len bytes\nremain in the buffer. The existing boundary check only validates the\n2 bits for get_bits(), not the subsequent 1-4 bytes that get_uint()\nreads. This allows a malformed H.323/RAS packet to cause a 1-4 byte\nslab-out-of-bounds read.\n\nAdd a boundary check for len bytes after get_bits() and before\nget_uint().","publishedAt":"2026-04-03T15:15:37.534Z","updatedAt":"2026-10-19T18:35:44.721Z","severity":{"score":8.2,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"5e35941d990123f155b02d5663e51a24f816b6f3","status":"affected","lessThan":"a2cd54b9348e485d338b3c132338a4410c99afaf","versionType":"git"},{"version":"5e35941d990123f155b02d5663e51a24f816b6f3","status":"affected","lessThan":"c95dc674ebf01ecfb40388b6facfc89b81fed3b7","versionType":"git"},{"version":"5e35941d990123f155b02d5663e51a24f816b6f3","status":"affected","lessThan":"41b417ff73a24b2c68134992cc44c88db27f482d","versionType":"git"},{"version":"5e35941d990123f155b02d5663e51a24f816b6f3","status":"affected","lessThan":"52235bf88159a1ef16434ab49e47e99c8a09ab20","versionType":"git"},{"version":"5e35941d990123f155b02d5663e51a24f816b6f3","status":"affected","lessThan":"774a434f8c9c8602a976b2536f65d0172a07f4d2","versionType":"git"},{"version":"5e35941d990123f155b02d5663e51a24f816b6f3","status":"affected","lessThan":"6bce72daeccca9aa1746e92d6c3d4784e71f2ebb","versionType":"git"},{"version":"5e35941d990123f155b02d5663e51a24f816b6f3","status":"affected","lessThan":"fb6c3596823ec5dd09c2123340330d7448f51a59","versionType":"git"},{"version":"5e35941d990123f155b02d5663e51a24f816b6f3","status":"affected","lessThan":"1e3a3593162c96e8a8de48b1e14f60c3b57fca8a","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/netfilter/nf_conntrack_h323_asn1.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"2.6.17","status":"affected"},{"version":"0","status":"unaffected","lessThan":"2.6.17","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":"6.1.167","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.130","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.78","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.20","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.10","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_h323_asn1.c"]}],"references":["https://git.kernel.org/stable/c/a2cd54b9348e485d338b3c132338a4410c99afaf","https://git.kernel.org/stable/c/c95dc674ebf01ecfb40388b6facfc89b81fed3b7","https://git.kernel.org/stable/c/41b417ff73a24b2c68134992cc44c88db27f482d","https://git.kernel.org/stable/c/52235bf88159a1ef16434ab49e47e99c8a09ab20","https://git.kernel.org/stable/c/774a434f8c9c8602a976b2536f65d0172a07f4d2","https://git.kernel.org/stable/c/6bce72daeccca9aa1746e92d6c3d4784e71f2ebb","https://git.kernel.org/stable/c/fb6c3596823ec5dd09c2123340330d7448f51a59","https://git.kernel.org/stable/c/1e3a3593162c96e8a8de48b1e14f60c3b57fca8a","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":["CWE-125"],"ingestedAt":"2026-10-29T20:11:21.040Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/23xxx/CVE-2026-23456.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-23456","state":"PUBLISHED","datePublished":"2026-04-03T15:15:37.534Z","dateUpdated":"2026-10-19T18:35:44.721Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-01-13T15:37:46.020Z"},"containers":{"cna":{"title":"netfilter: nf_conntrack_h323: fix OOB read in decode_int() CONS case","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nf_conntrack_h323: fix OOB read in decode_int() CONS case\n\nIn decode_int(), the CONS case calls get_bits(bs, 2) to read a length\nvalue, then calls get_uint(bs, len) without checking that len bytes\nremain in the buffer. The existing boundary check only validates the\n2 bits for get_bits(), not the subsequent 1-4 bytes that get_uint()\nreads. This allows a malformed H.323/RAS packet to cause a 1-4 byte\nslab-out-of-bounds read.\n\nAdd a boundary check for len bytes after get_bits() and before\nget_uint()."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"5e35941d990123f155b02d5663e51a24f816b6f3","status":"affected","lessThan":"a2cd54b9348e485d338b3c132338a4410c99afaf","versionType":"git"},{"version":"5e35941d990123f155b02d5663e51a24f816b6f3","status":"affected","lessThan":"c95dc674ebf01ecfb40388b6facfc89b81fed3b7","versionType":"git"},{"version":"5e35941d990123f155b02d5663e51a24f816b6f3","status":"affected","lessThan":"41b417ff73a24b2c68134992cc44c88db27f482d","versionType":"git"},{"version":"5e35941d990123f155b02d5663e51a24f816b6f3","status":"affected","lessThan":"52235bf88159a1ef16434ab49e47e99c8a09ab20","versionType":"git"},{"version":"5e35941d990123f155b02d5663e51a24f816b6f3","status":"affected","lessThan":"774a434f8c9c8602a976b2536f65d0172a07f4d2","versionType":"git"},{"version":"5e35941d990123f155b02d5663e51a24f816b6f3","status":"affected","lessThan":"6bce72daeccca9aa1746e92d6c3d4784e71f2ebb","versionType":"git"},{"version":"5e35941d990123f155b02d5663e51a24f816b6f3","status":"affected","lessThan":"fb6c3596823ec5dd09c2123340330d7448f51a59","versionType":"git"},{"version":"5e35941d990123f155b02d5663e51a24f816b6f3","status":"affected","lessThan":"1e3a3593162c96e8a8de48b1e14f60c3b57fca8a","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/netfilter/nf_conntrack_h323_asn1.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"2.6.17","status":"affected"},{"version":"0","status":"unaffected","lessThan":"2.6.17","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":"6.1.167","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.130","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.78","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.20","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.10","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_h323_asn1.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/a2cd54b9348e485d338b3c132338a4410c99afaf"},{"url":"https://git.kernel.org/stable/c/c95dc674ebf01ecfb40388b6facfc89b81fed3b7"},{"url":"https://git.kernel.org/stable/c/41b417ff73a24b2c68134992cc44c88db27f482d"},{"url":"https://git.kernel.org/stable/c/52235bf88159a1ef16434ab49e47e99c8a09ab20"},{"url":"https://git.kernel.org/stable/c/774a434f8c9c8602a976b2536f65d0172a07f4d2"},{"url":"https://git.kernel.org/stable/c/6bce72daeccca9aa1746e92d6c3d4784e71f2ebb"},{"url":"https://git.kernel.org/stable/c/fb6c3596823ec5dd09c2123340330d7448f51a59"},{"url":"https://git.kernel.org/stable/c/1e3a3593162c96e8a8de48b1e14f60c3b57fca8a"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H","baseScore":8.2,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:N - The vulnerable parser is reached by network-delivered H.323/RAS UDP traffic when the nf_conntrack_h323 RAS helper is active on a firewall/NAT gateway. A remote peer can supply the malformed packet payload that drives DecodeRasMessage() into decode_int().\nAC:L - The trigger is a deterministic malformed CONS integer where the 2-bit length claims 1-4 bytes that are not present. No race or attacker-external condition is required once the helper is attached to the flow.\nPR:N - The packet decoding path has no authentication or privilege check; it runs on received network traffic before any H.323 protocol-level trust decision. Helper configuration/loading may be administrative setup, but the attacker sending the malformed packet needs no privileges on the target.\nUI:N - Exploitation only requires sending crafted network traffic to a system processing H.323/RAS through conntrack. No victim user action is required.\nS:U - The impact is within the kernel/network filtering security authority of the affected system. There is no guest-to-host, sandbox, or separate authority boundary crossed.\nC:L - The bug is a bounded 1-4 byte slab out-of-bounds read from adjacent kernel memory. Because the read is strictly limited to a few bytes and not a broad arbitrary read primitive, confidentiality impact is limited.\nI:N - The flaw is an out-of-bounds read only; it does not write beyond bounds or corrupt kernel objects. The decoded value only affects existing H.323 conntrack timeout handling.\nA:H - A malformed unauthenticated packet can repeatedly trigger a slab out-of-bounds read in softirq packet processing, which can produce a KASAN/oops/panic on hardened or debug kernels. This is defensibly a high availability impact for affected deployments."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T12:21:55.155Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.17","versionEndExcluding":"5.10.253"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.17","versionEndExcluding":"5.15.203"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.17","versionEndExcluding":"6.1.167"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.17","versionEndExcluding":"6.6.130"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.17","versionEndExcluding":"6.12.78"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.17","versionEndExcluding":"6.18.20"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.17","versionEndExcluding":"6.19.10"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.17","versionEndExcluding":"7.0"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"affected":[{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.6","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.5","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.7","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.6","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.5","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.7","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.6","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.5","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.7","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.6","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.5","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.7","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIPLUS S7-1500 CPU 1518-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.6","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIPLUS S7-1500 CPU 1518-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.5","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIPLUS S7-1500 CPU 1518-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.7","status":"affected","lessThan":"*","versionType":"custom"}]}],"references":[{"url":"https://cert-portal.siemens.com/productcert/html/ssa-082556.html"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-019113.html"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-457936.html"}],"providerMetadata":{"shortName":"siemens-SADP","orgId":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e","dateUpdated":"2026-10-15T01:15:18.430Z"},"x_adpType":"supplier"},{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-23456","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"version":"2.0.3","timestamp":"2026-10-16T15:08:25.282768Z"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-125","lang":"en","type":"CWE","description":"CWE-125 Out-of-bounds Read"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-19T18:35:44.721Z"}}]}}}