{"api_version":"1","generated_at":"2026-08-23T21:53:22+00:00","cve":"CVE-2026-74621","urls":{"html":"https://cve.report/CVE-2026-74621","api":"https://cve.report/api/cve/CVE-2026-74621.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-74621","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-74621"},"summary":{"title":"net/sched: act_ct: fix sk_buff leak when the header checks reject a packet","description":"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.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-08-22 16:16:34","updated_at":"2026-08-23 13:16:47"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/b47bb899e04b5407c5a63fe88d4b6676586a6e84","name":"https://git.kernel.org/stable/c/b47bb899e04b5407c5a63fe88d4b6676586a6e84","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/439d3e404f9d5e515911cc8132cde198b337c19e","name":"https://git.kernel.org/stable/c/439d3e404f9d5e515911cc8132cde198b337c19e","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/b5dbecc2016e1692fd1c2532af9c41ba729cb747","name":"https://git.kernel.org/stable/c/b5dbecc2016e1692fd1c2532af9c41ba729cb747","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/47d99828591d0fe8be4b9c8992ff3b8e47968db9","name":"https://git.kernel.org/stable/c/47d99828591d0fe8be4b9c8992ff3b8e47968db9","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/737873a59905a54ca0d2d127ef882f3f88bf4379","name":"https://git.kernel.org/stable/c/737873a59905a54ca0d2d127ef882f3f88bf4379","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/23e97d594ddd0153020c506d5041048fbde1beb4","name":"https://git.kernel.org/stable/c/23e97d594ddd0153020c506d5041048fbde1beb4","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/8a7ed561671aa6a911a2de99e59ef670a4d0b1df","name":"https://git.kernel.org/stable/c/8a7ed561671aa6a911a2de99e59ef670a4d0b1df","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-74621","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-74621","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 172ba7d46c202e679f3ccb10264c67416aaeb1c4 b5dbecc2016e1692fd1c2532af9c41ba729cb747 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 0b5b831122fc3789fff75be433ba3e4dd7b779d4 23e97d594ddd0153020c506d5041048fbde1beb4 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 73f7da5fd124f2cda9161e2e46114915e6e82e97 737873a59905a54ca0d2d127ef882f3f88bf4379 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 3f14b377d01d8357eba032b4cabc8c1149b458b6 47d99828591d0fe8be4b9c8992ff3b8e47968db9 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 3f14b377d01d8357eba032b4cabc8c1149b458b6 b47bb899e04b5407c5a63fe88d4b6676586a6e84 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 3f14b377d01d8357eba032b4cabc8c1149b458b6 439d3e404f9d5e515911cc8132cde198b337c19e git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 3f14b377d01d8357eba032b4cabc8c1149b458b6 8a7ed561671aa6a911a2de99e59ef670a4d0b1df git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected f5346df0591d10bc948761ca854b1fae6d2ef441 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 5.15.148 5.15.217 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6.1.75 6.1.184 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6.6.14 6.6.152 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6.7.2 6.8 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6.8","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.8 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 5.15.217 5.15.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.1.184 6.1.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.6.152 6.6.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.104 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.45 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.1.9 7.1.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.2 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["net/sched/act_ct.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"b5dbecc2016e1692fd1c2532af9c41ba729cb747","status":"affected","version":"172ba7d46c202e679f3ccb10264c67416aaeb1c4","versionType":"git"},{"lessThan":"23e97d594ddd0153020c506d5041048fbde1beb4","status":"affected","version":"0b5b831122fc3789fff75be433ba3e4dd7b779d4","versionType":"git"},{"lessThan":"737873a59905a54ca0d2d127ef882f3f88bf4379","status":"affected","version":"73f7da5fd124f2cda9161e2e46114915e6e82e97","versionType":"git"},{"lessThan":"47d99828591d0fe8be4b9c8992ff3b8e47968db9","status":"affected","version":"3f14b377d01d8357eba032b4cabc8c1149b458b6","versionType":"git"},{"lessThan":"b47bb899e04b5407c5a63fe88d4b6676586a6e84","status":"affected","version":"3f14b377d01d8357eba032b4cabc8c1149b458b6","versionType":"git"},{"lessThan":"439d3e404f9d5e515911cc8132cde198b337c19e","status":"affected","version":"3f14b377d01d8357eba032b4cabc8c1149b458b6","versionType":"git"},{"lessThan":"8a7ed561671aa6a911a2de99e59ef670a4d0b1df","status":"affected","version":"3f14b377d01d8357eba032b4cabc8c1149b458b6","versionType":"git"},{"status":"affected","version":"f5346df0591d10bc948761ca854b1fae6d2ef441","versionType":"git"},{"lessThan":"5.15.217","status":"affected","version":"5.15.148","versionType":"semver"},{"lessThan":"6.1.184","status":"affected","version":"6.1.75","versionType":"semver"},{"lessThan":"6.6.152","status":"affected","version":"6.6.14","versionType":"semver"},{"lessThan":"6.8","status":"affected","version":"6.7.2","versionType":"semver"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["net/sched/act_ct.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"6.8"},{"lessThan":"6.8","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"5.15.*","status":"unaffected","version":"5.15.217","versionType":"semver"},{"lessThanOrEqual":"6.1.*","status":"unaffected","version":"6.1.184","versionType":"semver"},{"lessThanOrEqual":"6.6.*","status":"unaffected","version":"6.6.152","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.104","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.45","versionType":"semver"},{"lessThanOrEqual":"7.1.*","status":"unaffected","version":"7.1.9","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.2","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"5.15.217","versionStartIncluding":"5.15.148","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.1.184","versionStartIncluding":"6.1.75","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.6.152","versionStartIncluding":"6.6.14","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.12.104","versionStartIncluding":"6.8","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.45","versionStartIncluding":"6.8","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.1.9","versionStartIncluding":"6.8","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2","versionStartIncluding":"6.8","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.7.2","vulnerable":true}],"negate":false,"operator":"OR"}]}],"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."}],"providerMetadata":{"dateUpdated":"2026-08-23T12:47:47.471Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/b5dbecc2016e1692fd1c2532af9c41ba729cb747"},{"url":"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"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-74621","datePublished":"2026-08-22T15:32:04.990Z","dateReserved":"2026-08-15T05:44:03.921Z","dateUpdated":"2026-08-23T12:47:47.471Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-08-22 16:16:34","lastModifiedDate":"2026-08-23 13:16:47","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"74621","Ordinal":"1","Title":"net/sched: act_ct: fix sk_buff leak when the header checks rejec","CVE":"CVE-2026-74621","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"74621","Ordinal":"1","NoteData":"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.","Type":"Description","Title":"net/sched: act_ct: fix sk_buff leak when the header checks rejec"}]}}}