{"api_version":"1","generated_at":"2026-08-24T20:08:14+00:00","cve":"CVE-2026-72347","urls":{"html":"https://cve.report/CVE-2026-72347","api":"https://cve.report/api/cve/CVE-2026-72347.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-72347","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-72347"},"summary":{"title":"netfilter: xt_connmark: reject invalid shift parameters","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: xt_connmark: reject invalid shift parameters\n\nRevision 2 of the CONNMARK target accepts user-controlled shift\nparameters and applies them to 32-bit mark values in\nconnmark_tg_shift().\n\nA shift_bits value of 32 or more triggers an undefined-shift bug when\nthe rule is evaluated. Invalid shift_dir values are also accepted and\nsilently fall back to the left-shift path.\n\nReject invalid revision-2 shift parameters in connmark_tg_check() so\nmalformed rules fail at installation time, before they can reach the\npacket path.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-08-15 06:22:08","updated_at":"2026-08-17 06:18:38"},"problem_types":[],"metrics":[{"version":"3.1","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","score":"7.3","severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:H","data":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:H","baseScore":7.3,"baseSeverity":"HIGH","attackVector":"LOCAL","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"LOW","integrityImpact":"HIGH","availabilityImpact":"HIGH"}},{"version":"3.1","source":"CNA","type":"DECLARED","score":"7.3","severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:H","data":{"baseScore":7.3,"baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:H","version":"3.1"}}],"references":[{"url":"https://git.kernel.org/stable/c/d8ce63d928b457fba7ed1e302492dfd32293671c","name":"https://git.kernel.org/stable/c/d8ce63d928b457fba7ed1e302492dfd32293671c","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/9657bb11a6376ab0a79f05d433713d6944111e9d","name":"https://git.kernel.org/stable/c/9657bb11a6376ab0a79f05d433713d6944111e9d","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/8ace320ac4416f5e5fbcd065309fb2dfcce787b0","name":"https://git.kernel.org/stable/c/8ace320ac4416f5e5fbcd065309fb2dfcce787b0","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/4eef84b09a3836919360c4232b0f16651a155eec","name":"https://git.kernel.org/stable/c/4eef84b09a3836919360c4232b0f16651a155eec","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/230173cc6105bdfb2696d37e6e56687b003fbe63","name":"https://git.kernel.org/stable/c/230173cc6105bdfb2696d37e6e56687b003fbe63","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/c3fa852d117b3fda72265e4230e3967db4a74fcf","name":"https://git.kernel.org/stable/c/c3fa852d117b3fda72265e4230e3967db4a74fcf","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/1b47026fb4b35bac850ad6e8a4ad7fc018e09ebc","name":"https://git.kernel.org/stable/c/1b47026fb4b35bac850ad6e8a4ad7fc018e09ebc","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-72347","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-72347","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 472a73e00757b971d613d796374d2727b2e4954d d8ce63d928b457fba7ed1e302492dfd32293671c git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 472a73e00757b971d613d796374d2727b2e4954d 9657bb11a6376ab0a79f05d433713d6944111e9d git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 472a73e00757b971d613d796374d2727b2e4954d 8ace320ac4416f5e5fbcd065309fb2dfcce787b0 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 472a73e00757b971d613d796374d2727b2e4954d c3fa852d117b3fda72265e4230e3967db4a74fcf git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 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the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: xt_connmark: reject invalid shift parameters\n\nRevision 2 of the CONNMARK target accepts user-controlled shift\nparameters and applies them to 32-bit mark values in\nconnmark_tg_shift().\n\nA shift_bits value of 32 or more triggers an undefined-shift bug when\nthe rule is evaluated. Invalid shift_dir values are also accepted and\nsilently fall back to the left-shift path.\n\nReject invalid revision-2 shift parameters in connmark_tg_check() so\nmalformed rules fail at installation time, before they can reach the\npacket path."}],"metrics":[{"cvssV3_1":{"baseScore":7.3,"baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:H","version":"3.1"},"scenarios":[{"lang":"en","value":"AV:L - Malformed CONNMARK rev2 rules are installed via IPT_SO_SET_REPLACE setsockopt or nftables NFNetlink (nft_compat); per kernel CNA guidance netfilter/xtables rule setup is Local even though installed rules later evaluate on ingress/egress packets through ipt_do_table/ip6t_do_table.\nAC:L - The attacker fully controls shift_bits and shift_dir in xt_connmark_tginfo2 when installing the rev2 CONNMARK target and can send conntrack-tracked packets to reliably hit connmark_tg_shift(); no race, memory layout, or victim state outside attacker control is required.\nPR:L - Installing CONNMARK iptables/nftables rules requires CAP_NET_ADMIN in the target network namespace, obtainable by unprivileged users via unshare -Urn; ip_tables.c do_ipt_set_ctl() and nfnetlink.c nfnetlink_rcv() enforce ns_capable/netlink_net_capable against the namespace user_ns.\nUI:N - The attacker installs the malformed CONNMARK rev2 rule and generates matching conntrack-associated traffic in their namespace; no separate victim action such as opening files, mounting media, or clicking links is required.\nS:U - Undefined shift during xt_CONNMARK packet targeting and resulting mark corruption remain within the host kernel security authority; this is standard local kernel netfilter compromise, not a VM escape, IOMMU bypass, or sandbox boundary crossing.\nC:L - Undefined-behavior shifts on 32-bit mark values produce attacker-influenced unpredictable ct->mark and skb->mark results observable through conntrack netlink and mark-based iptables/nftables matches, leaking altered connection-classification state within the namespace.\nI:H - Invalid shift_bits or shift_dir corrupt connmark_tg_shift() output written to nf_conn->mark and skb->mark, subverting mark-dependent firewall, policy-routing, QoS, and multi-tenant container egress controls on cloud routers and internet-facing servers.\nA:H - Evaluating a malformed CONNMARK rev2 rule with shift_bits>=32 triggers C11 undefined-shift UB in connmark_tg_shift() during softirq netfilter processing; UBSAN-instrumented kernels panic on shift-out-of-bounds, and UB in the packet hot path can destabilize conntrack-driven forwarding."}]}],"providerMetadata":{"dateUpdated":"2026-08-17T05:43:05.530Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/d8ce63d928b457fba7ed1e302492dfd32293671c"},{"url":"https://git.kernel.org/stable/c/9657bb11a6376ab0a79f05d433713d6944111e9d"},{"url":"https://git.kernel.org/stable/c/8ace320ac4416f5e5fbcd065309fb2dfcce787b0"},{"url":"https://git.kernel.org/stable/c/c3fa852d117b3fda72265e4230e3967db4a74fcf"},{"url":"https://git.kernel.org/stable/c/4eef84b09a3836919360c4232b0f16651a155eec"},{"url":"https://git.kernel.org/stable/c/230173cc6105bdfb2696d37e6e56687b003fbe63"},{"url":"https://git.kernel.org/stable/c/1b47026fb4b35bac850ad6e8a4ad7fc018e09ebc"}],"title":"netfilter: xt_connmark: reject invalid shift parameters","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-72347","datePublished":"2026-08-15T05:55:51.665Z","dateReserved":"2026-08-09T03:40:39.920Z","dateUpdated":"2026-08-17T05:43:05.530Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-08-15 06:22:08","lastModifiedDate":"2026-08-17 06:18:38","problem_types":[],"metrics":{"cvssMetricV31":[{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:H","baseScore":7.3,"baseSeverity":"HIGH","attackVector":"LOCAL","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"LOW","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":1.8,"impactScore":5.5}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"72347","Ordinal":"1","Title":"netfilter: xt_connmark: reject invalid shift parameters","CVE":"CVE-2026-72347","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"72347","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: xt_connmark: reject invalid shift parameters\n\nRevision 2 of the CONNMARK target accepts user-controlled shift\nparameters and applies them to 32-bit mark values in\nconnmark_tg_shift().\n\nA shift_bits value of 32 or more triggers an undefined-shift bug when\nthe rule is evaluated. Invalid shift_dir values are also accepted and\nsilently fall back to the left-shift path.\n\nReject invalid revision-2 shift parameters in connmark_tg_check() so\nmalformed rules fail at installation time, before they can reach the\npacket path.","Type":"Description","Title":"netfilter: xt_connmark: reject invalid shift parameters"}]}}}