{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-72347", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-08-09T03:40:39.920Z", "datePublished": "2026-08-15T05:55:51.665Z", "dateUpdated": "2026-08-17T05:43:05.530Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-17T05:43:05.530Z" }, "descriptions": [ { "lang": "en", "value": "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." } ], "metrics": [ { "cvssV3_1": { "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" }, "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." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/netfilter/xt_connmark.c" ], "versions": [ { "version": "472a73e00757b971d613d796374d2727b2e4954d", "lessThan": "d8ce63d928b457fba7ed1e302492dfd32293671c", "status": "affected", "versionType": "git" }, { "version": "472a73e00757b971d613d796374d2727b2e4954d", "lessThan": "9657bb11a6376ab0a79f05d433713d6944111e9d", "status": "affected", "versionType": "git" }, { "version": "472a73e00757b971d613d796374d2727b2e4954d", "lessThan": "8ace320ac4416f5e5fbcd065309fb2dfcce787b0", "status": "affected", "versionType": "git" }, { "version": "472a73e00757b971d613d796374d2727b2e4954d", "lessThan": "c3fa852d117b3fda72265e4230e3967db4a74fcf", "status": "affected", "versionType": "git" }, { "version": "472a73e00757b971d613d796374d2727b2e4954d", "lessThan": "4eef84b09a3836919360c4232b0f16651a155eec", "status": "affected", "versionType": "git" }, { "version": "472a73e00757b971d613d796374d2727b2e4954d", "lessThan": "230173cc6105bdfb2696d37e6e56687b003fbe63", "status": "affected", "versionType": "git" }, { "version": "472a73e00757b971d613d796374d2727b2e4954d", "lessThan": "1b47026fb4b35bac850ad6e8a4ad7fc018e09ebc", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/netfilter/xt_connmark.c" ], "versions": [ { "version": "4.17", "status": "affected" }, { "version": "0", "lessThan": "4.17", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.212", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.178", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.145", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.97", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.40", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1.5", "lessThanOrEqual": "7.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.17", "versionEndExcluding": "5.15.212" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.17", "versionEndExcluding": "6.1.178" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.17", "versionEndExcluding": "6.6.145" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.17", "versionEndExcluding": "6.12.97" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.17", "versionEndExcluding": "6.18.40" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.17", "versionEndExcluding": "7.1.5" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.17", "versionEndExcluding": "7.2" } ] } ] } ], "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" } } } }