{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-74621", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-08-15T05:44:03.921Z", "datePublished": "2026-08-22T15:32:04.990Z", "dateUpdated": "2026-10-16T19:06:02.607Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-25T05:40:45.894Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: act_ct: fix sk_buff leak when the header checks reject a packet\n\ntcf_ct_handle_fragments() runs its header sanity checks before handing\nanything to the defragmentation engine:\n\n\tif (family == NFPROTO_IPV4)\n\t\terr = tcf_ct_ipv4_is_fragment(skb, &frag);\n\telse\n\t\terr = tcf_ct_ipv6_is_fragment(skb, &frag);\n\tif (err || !frag)\n\t\treturn err;\n\ntcf_ct_ipv4_is_fragment() returns -EINVAL or -ENOMEM;\ntcf_ct_ipv6_is_fragment() adds -EPROTO when ipv6_find_hdr() fails. None of\nthem frees or queues the skb, so on that path the caller still owns it.\n\ntcf_ct_act() however funnels every non-zero return into the\nownership-transfer exit:\n\n\terr = tcf_ct_handle_fragments(net, skb, family, p->zone, &defrag);\n\tif (err)\n\t\tgoto out_frag;\n\t...\nout_frag:\n\tif (err != -EINPROGRESS)\n\t\ttcf_action_inc_drop_qstats(&c->common);\n\treturn TC_ACT_CONSUMED;\n\nTC_ACT_CONSUMED means the action took ownership of the skb, so no caller\nfrees it - sch_handle_ingress(), sch_handle_egress() and\ntcf_qevent_handle() all deliberately skip the free for that verdict. The\nskb is therefore orphaned: one sk_buff plus its data buffer is leaked per\nmalformed packet, unbounded. Note the drop counter is already incremented\nfor these errors, so the statistics claim a drop that never happens.\n\nThree different ownership states reach out_frag: today - the skb may be\nqueued by the defrag engine (-EINPROGRESS), already freed by\nnf_ct_handle_fragments(), or still owned by us. Tell the caller which of\nthose it is, and free the packet ourselves in the last case, which\nrestores the TC_ACT_SHOT behaviour that predated the Fixes: commit.\n\nReproduced on v7.2-rc6 with a 54-byte frame carrying a 40-byte IPv6\nheader with nexthdr = 0 (hop-by-hop) and nothing after it, on a\nclsact ingress chain with \"action ct\". kmemleak reports one leaked\n232-byte skbuff_head_cache object plus its 704-byte data buffer per\npacket; with this patch it reports none." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "baseScore": 7.5, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:N - The leak is triggered in tcf_ct_act() on the packet datapath (netif_receive_skb → sch_handle_ingress/egress → tc_run → tcf_classify); on OVN/Kubernetes/SDN gateways and mlx5-offload nodes with act_ct on clsact, a remote peer sends malformed IP packets with no local access required.\nAC:L - The attacker fully controls packet contents; a 54-byte IPv6 frame with nexthdr=0 (hop-by-hop) and no trailing data deterministically makes ipv6_find_hdr() return -EPROTO, leaking one skb per packet without races or uncontrollable layout dependencies.\nPR:N - Installing act_ct requires CAP_NET_ADMIN, but triggering the leak on an already-configured internet-facing or tenant-facing gateway needs no target credentials; a remote attacker only sends crafted malformed IP packets, matching CNA precedent for packet-driven act_ct issues (e.g., CVE-2026-72057).\nUI:N - Exploitation requires only attacker-generated malformed packets reaching a host with act_ct on clsact/ingress or egress; no victim login, mount, or other interactive action is needed beyond normal network traffic processing.\nS:U - The leaked sk_buff objects remain within the host kernel memory domain; this is not a VM escape, sandbox breakout, or IOMMU boundary bypass, only unbounded kernel heap consumption on the affected node.\nC:N - This is a pure sk_buff ownership leak on an error path; skb memory is orphaned, not exposed to the attacker, with no out-of-bounds read, use-after-free, or other disclosure primitive.\nI:N - The flaw only fails to kfree_skb() when header validation rejects a packet; it does not corrupt, overwrite, or modify any memory contents and provides no write or code-execution primitive.\nA:H - Each malformed packet leaks one sk_buff plus its data buffer (~936 bytes); sustained remote flooding causes unbounded kernel memory exhaustion and OOM denial of service, matching CNA precedent for repeatable network-triggered skb leaks (e.g., CVE-2026-52974)." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/sched/act_ct.c" ], "versions": [ { "version": "172ba7d46c202e679f3ccb10264c67416aaeb1c4", "lessThan": "b5dbecc2016e1692fd1c2532af9c41ba729cb747", "status": "affected", "versionType": "git" }, { "version": "0b5b831122fc3789fff75be433ba3e4dd7b779d4", "lessThan": "23e97d594ddd0153020c506d5041048fbde1beb4", "status": "affected", "versionType": "git" }, { "version": "73f7da5fd124f2cda9161e2e46114915e6e82e97", "lessThan": "737873a59905a54ca0d2d127ef882f3f88bf4379", "status": "affected", "versionType": "git" }, { "version": "3f14b377d01d8357eba032b4cabc8c1149b458b6", "lessThan": "47d99828591d0fe8be4b9c8992ff3b8e47968db9", "status": "affected", "versionType": "git" }, { "version": "3f14b377d01d8357eba032b4cabc8c1149b458b6", "lessThan": "b47bb899e04b5407c5a63fe88d4b6676586a6e84", "status": "affected", "versionType": "git" }, { "version": "3f14b377d01d8357eba032b4cabc8c1149b458b6", "lessThan": "439d3e404f9d5e515911cc8132cde198b337c19e", "status": "affected", "versionType": "git" }, { "version": "3f14b377d01d8357eba032b4cabc8c1149b458b6", "lessThan": "8a7ed561671aa6a911a2de99e59ef670a4d0b1df", "status": "affected", "versionType": "git" }, { "version": "f5346df0591d10bc948761ca854b1fae6d2ef441", "status": "affected", "versionType": "git" }, { "version": "5.15.148", "lessThan": "5.15.217", "status": "affected", "versionType": "semver" }, { "version": "6.1.75", "lessThan": "6.1.184", "status": "affected", "versionType": "semver" }, { "version": "6.6.14", "lessThan": "6.6.152", "status": "affected", "versionType": "semver" }, { "version": "6.7.2", "lessThan": "6.8", "status": "affected", "versionType": "semver" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/sched/act_ct.c" ], "versions": [ { "version": "6.8", "status": "affected" }, { "version": "0", "lessThan": "6.8", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.217", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.184", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.152", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.104", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.45", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1.9", "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": "5.15.148", "versionEndExcluding": "5.15.217" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.1.75", "versionEndExcluding": "6.1.184" }, { "vulnerable": true, "criteria": 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"https://git.kernel.org/stable/c/23e97d594ddd0153020c506d5041048fbde1beb4" }, { "url": "https://git.kernel.org/stable/c/737873a59905a54ca0d2d127ef882f3f88bf4379" }, { "url": "https://git.kernel.org/stable/c/47d99828591d0fe8be4b9c8992ff3b8e47968db9" }, { "url": "https://git.kernel.org/stable/c/b47bb899e04b5407c5a63fe88d4b6676586a6e84" }, { "url": "https://git.kernel.org/stable/c/439d3e404f9d5e515911cc8132cde198b337c19e" }, { "url": "https://git.kernel.org/stable/c/8a7ed561671aa6a911a2de99e59ef670a4d0b1df" } ], "title": "net/sched: act_ct: fix sk_buff leak when the header checks reject a packet", "x_generator": { "engine": "bippy-1.2.0" } }, "adp": [ { "metrics": [ { "other": { "type": "ssvc", "content": { "id": "CVE-2026-74621", "role": "CISA Coordinator", "options": [ { "Exploitation": "none" }, { "Automatable": "yes" }, { "Technical Impact": "partial" } ], "version": "2.0.3", "timestamp": "2026-10-16T19:02:40.438798Z" } } } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { 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