{"id":"CVE-2026-43026","state":"PUBLISHED","title":"netfilter: ctnetlink: zero expect NAT fields when CTA_EXPECT_NAT absent","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: ctnetlink: zero expect NAT fields when CTA_EXPECT_NAT absent\n\nctnetlink_alloc_expect() allocates expectations from a non-zeroing\nslab cache via nf_ct_expect_alloc().  When CTA_EXPECT_NAT is not\npresent in the netlink message, saved_addr and saved_proto are\nnever initialized.  Stale data from a previous slab occupant can\nthen be dumped to userspace by ctnetlink_exp_dump_expect(), which\nchecks these fields to decide whether to emit CTA_EXPECT_NAT.\n\nThe safe sibling nf_ct_expect_init(), used by the packet path,\nexplicitly zeroes these fields.\n\nZero saved_addr, saved_proto and dir in the else branch, guarded\nby IS_ENABLED(CONFIG_NF_NAT) since these fields only exist when\nNAT is enabled.\n\nConfirmed by priming the expect slab with NAT-bearing expectations,\nfreeing them, creating a new expectation without CTA_EXPECT_NAT,\nand observing that the ctnetlink dump emits a spurious\nCTA_EXPECT_NAT containing stale data from the prior allocation.","publishedAt":"2026-05-01T14:15:27.854Z","updatedAt":"2026-10-15T01:18:39.379Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"076a0ca02644657b13e4af363f487ced2942e9cb","status":"affected","lessThan":"a5a89db6981a1ddf2314bf50cb49db5a3146185f","versionType":"git"},{"version":"076a0ca02644657b13e4af363f487ced2942e9cb","status":"affected","lessThan":"1c2ebdeff8d088a2e47ae25d7b38447249adace2","versionType":"git"},{"version":"076a0ca02644657b13e4af363f487ced2942e9cb","status":"affected","lessThan":"a64b7bf84b4d5ea54218c5d374ec87fff9000f43","versionType":"git"},{"version":"076a0ca02644657b13e4af363f487ced2942e9cb","status":"affected","lessThan":"2898080c054ea4d6ddfaaf21bbedbc229a9a8376","versionType":"git"},{"version":"076a0ca02644657b13e4af363f487ced2942e9cb","status":"affected","lessThan":"fd002ff2ea030cbfb0188a11b3c60ce7f84485f4","versionType":"git"},{"version":"076a0ca02644657b13e4af363f487ced2942e9cb","status":"affected","lessThan":"929f7a9a7aad9404a5867216c3f8738232355b38","versionType":"git"},{"version":"076a0ca02644657b13e4af363f487ced2942e9cb","status":"affected","lessThan":"bff0f4f06f12d6d9bc565a3e1378abd4f6f5ce36","versionType":"git"},{"version":"076a0ca02644657b13e4af363f487ced2942e9cb","status":"affected","lessThan":"35177c6877134a21315f37d57a5577846225623e","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/netfilter/nf_conntrack_netlink.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"3.4","status":"affected"},{"version":"0","status":"unaffected","lessThan":"3.4","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":"6.6.134","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.81","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.22","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.12","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_netlink.c"]}],"references":["https://git.kernel.org/stable/c/a5a89db6981a1ddf2314bf50cb49db5a3146185f","https://git.kernel.org/stable/c/1c2ebdeff8d088a2e47ae25d7b38447249adace2","https://git.kernel.org/stable/c/a64b7bf84b4d5ea54218c5d374ec87fff9000f43","https://git.kernel.org/stable/c/2898080c054ea4d6ddfaaf21bbedbc229a9a8376","https://git.kernel.org/stable/c/fd002ff2ea030cbfb0188a11b3c60ce7f84485f4","https://git.kernel.org/stable/c/929f7a9a7aad9404a5867216c3f8738232355b38","https://git.kernel.org/stable/c/bff0f4f06f12d6d9bc565a3e1378abd4f6f5ce36","https://git.kernel.org/stable/c/35177c6877134a21315f37d57a5577846225623e","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":"2026-10-29T20:11:57.932Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/43xxx/CVE-2026-43026.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-43026","state":"PUBLISHED","datePublished":"2026-05-01T14:15:27.854Z","dateUpdated":"2026-10-15T01:18:39.379Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-05-01T14:12:55.976Z"},"containers":{"cna":{"title":"netfilter: ctnetlink: zero expect NAT fields when CTA_EXPECT_NAT absent","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: ctnetlink: zero expect NAT fields when CTA_EXPECT_NAT absent\n\nctnetlink_alloc_expect() allocates expectations from a non-zeroing\nslab cache via nf_ct_expect_alloc().  When CTA_EXPECT_NAT is not\npresent in the netlink message, saved_addr and saved_proto are\nnever initialized.  Stale data from a previous slab occupant can\nthen be dumped to userspace by ctnetlink_exp_dump_expect(), which\nchecks these fields to decide whether to emit CTA_EXPECT_NAT.\n\nThe safe sibling nf_ct_expect_init(), used by the packet path,\nexplicitly zeroes these fields.\n\nZero saved_addr, saved_proto and dir in the else branch, guarded\nby IS_ENABLED(CONFIG_NF_NAT) since these fields only exist when\nNAT is enabled.\n\nConfirmed by priming the expect slab with NAT-bearing expectations,\nfreeing them, creating a new expectation without CTA_EXPECT_NAT,\nand observing that the ctnetlink dump emits a spurious\nCTA_EXPECT_NAT containing stale data from the prior allocation."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"076a0ca02644657b13e4af363f487ced2942e9cb","status":"affected","lessThan":"a5a89db6981a1ddf2314bf50cb49db5a3146185f","versionType":"git"},{"version":"076a0ca02644657b13e4af363f487ced2942e9cb","status":"affected","lessThan":"1c2ebdeff8d088a2e47ae25d7b38447249adace2","versionType":"git"},{"version":"076a0ca02644657b13e4af363f487ced2942e9cb","status":"affected","lessThan":"a64b7bf84b4d5ea54218c5d374ec87fff9000f43","versionType":"git"},{"version":"076a0ca02644657b13e4af363f487ced2942e9cb","status":"affected","lessThan":"2898080c054ea4d6ddfaaf21bbedbc229a9a8376","versionType":"git"},{"version":"076a0ca02644657b13e4af363f487ced2942e9cb","status":"affected","lessThan":"fd002ff2ea030cbfb0188a11b3c60ce7f84485f4","versionType":"git"},{"version":"076a0ca02644657b13e4af363f487ced2942e9cb","status":"affected","lessThan":"929f7a9a7aad9404a5867216c3f8738232355b38","versionType":"git"},{"version":"076a0ca02644657b13e4af363f487ced2942e9cb","status":"affected","lessThan":"bff0f4f06f12d6d9bc565a3e1378abd4f6f5ce36","versionType":"git"},{"version":"076a0ca02644657b13e4af363f487ced2942e9cb","status":"affected","lessThan":"35177c6877134a21315f37d57a5577846225623e","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/netfilter/nf_conntrack_netlink.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"3.4","status":"affected"},{"version":"0","status":"unaffected","lessThan":"3.4","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":"6.6.134","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.81","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.22","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.12","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_netlink.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/a5a89db6981a1ddf2314bf50cb49db5a3146185f"},{"url":"https://git.kernel.org/stable/c/1c2ebdeff8d088a2e47ae25d7b38447249adace2"},{"url":"https://git.kernel.org/stable/c/a64b7bf84b4d5ea54218c5d374ec87fff9000f43"},{"url":"https://git.kernel.org/stable/c/2898080c054ea4d6ddfaaf21bbedbc229a9a8376"},{"url":"https://git.kernel.org/stable/c/fd002ff2ea030cbfb0188a11b3c60ce7f84485f4"},{"url":"https://git.kernel.org/stable/c/929f7a9a7aad9404a5867216c3f8738232355b38"},{"url":"https://git.kernel.org/stable/c/bff0f4f06f12d6d9bc565a3e1378abd4f6f5ce36"},{"url":"https://git.kernel.org/stable/c/35177c6877134a21315f37d57a5577846225623e"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-05-11T22:16:16.846Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.4","versionEndExcluding":"5.10.253"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.4","versionEndExcluding":"5.15.203"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.4","versionEndExcluding":"6.1.168"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.4","versionEndExcluding":"6.6.134"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.4","versionEndExcluding":"6.12.81"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.4","versionEndExcluding":"6.18.22"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.4","versionEndExcluding":"6.19.12"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"3.4","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":"2026-10-15T01:18:39.379Z"},"x_adpType":"supplier"}]}}}