{"cve":"CVE-2026-74621","nvd":{"published":"2026-08-22T16:16:34.897","modified":"2026-10-16T20:17:47.303","status":"Received","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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5},"cwes":[],"references":["https://git.kernel.org/stable/c/23e97d594ddd0153020c506d5041048fbde1beb4","https://git.kernel.org/stable/c/439d3e404f9d5e515911cc8132cde198b337c19e","https://git.kernel.org/stable/c/47d99828591d0fe8be4b9c8992ff3b8e47968db9","https://git.kernel.org/stable/c/737873a59905a54ca0d2d127ef882f3f88bf4379","https://git.kernel.org/stable/c/8a7ed561671aa6a911a2de99e59ef670a4d0b1df"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:49:38.260478770+00:00"},"epss":{"cve":"CVE-2026-74621","score":0.0049,"percentile":0.41831,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}