CVE-2026-74621

CVE CVE-2026-74621EUVD EUVD-2026-64558Published 2026-08-22T15:32:04.000ZLast changed 2026-08-25T05:40:45.000ZCVSS 7.5

What the advisory describes

In the Linux kernel, the following vulnerability has been resolved: net/sched: act_ct: fix sk_buff leak when the header checks reject a packet tcf_ct_handle_fragments() runs its header sanity checks before handing anything to the defragmentation engine: if (family == NFPROTO_IPV4) err = tcf_ct_ipv4_is_fragment(skb, &frag); else err = tcf_ct_ipv6_is_fragment(skb, &frag); if (err || !frag) return err; tcf_ct_ipv4_is_fragment() returns -EINVAL or -ENOMEM; tcf_ct_ipv6_is_fragment() adds -EPROTO when ipv6_find_hdr() fails. None of them frees or queues the skb, so on that path the caller still owns it. tcf_ct_act() however funnels every non-zero return into the ownership-transfer exit: err = tcf_ct_handle_fragments(net, skb, family, p->zone, &defrag); if (err) goto out_frag; ... out_frag: if (err != -EINPROGRESS) tcf_action_inc_drop_qstats(&c->common); return TC_ACT_CONSUMED; TC_ACT_CONSUMED means the action took ownership of the skb, so no caller frees it - sch_handle_ingress(), sch_handle_egress() and tcf_qevent_handle() all deliberately skip the free for that verdict. The skb is therefore orphaned: one sk_buff plus its data buffer is leaked per malformed packet, unbounded. Note the drop counter is already incremented for these errors, so the statistics claim a drop that never happens. Three different ownership states reach out_frag: today - the skb may be queued by the defrag engine (-EINPROGRESS), already freed by nf_ct_handle_fragments(), or still owned by us. Tell the caller which of those it is, and free the packet ourselves in the last case, which restores the TC_ACT_SHOT behaviour that predated the Fixes: commit. Reproduced on v7.2-rc6 with a 54-byte frame carrying a 40-byte IPv6 header with nexthdr = 0 (hop-by-hop) and nothing after it, on a clsact ingress chain with "action ct". kmemleak reports one leaked 232-byte skbuff_head_cache object plus its 704-byte data buffer per packet; with this patch it reports none.

Source: EUVD (ENISA), in the words of the advisory.

Products the advisory names

These come from the advisory itself, not from any check we performed.

• Linux — Linux 3f14b377d01d8357eba032b4cabc8c1149b458b6 <b47bb899e04b5407c5a63fe88d4b6676586a6e84; patch: 7.1.9; patch: 6.12.104; patch: 7.2; 3f14b377d01d8357eba032b4cabc8c1149b458b6 <439d3e404f9d5e515911cc8132cde198b337c19e; 73f7da5fd124f2cda9161e2e46114915e6e82e97 <737873a59905a54ca0d2d127ef882f3f88bf4379; patch: 6.1.184; 6.1.75 <6.1.184; patch: 6.6.152; 6.6.14 <6.6.152; 172ba7d46c202e679f3ccb10264c67416aaeb1c4 <b5dbecc2016e1692fd1c2532af9c41ba729cb747; 5.15.148 <5.15.217; 3f14b377d01d8357eba032b4cabc8c1149b458b6 <8a7ed561671aa6a911a2de99e59ef670a4d0b1df; patch: 0; patch: 5.15.217; 3f14b377d01d8357eba032b4cabc8c1149b458b6 <47d99828591d0fe8be4b9c8992ff3b8e47968db9; f5346df0591d10bc948761ca854b1fae6d2ef441; 6.7.2 <6.8; 6.8; patch: 6.18.45; 0b5b831122fc3789fff75be433ba3e4dd7b779d4 <23e97d594ddd0153020c506d5041048fbde1beb4

The versions shown are the advisory's own. Patchlage compares no version numbers and derives no judgement from them — which version is installed is something a person has to look up.

Carried in the product catalogue

An estate covering these products can be recorded in Patchlage. An advisory about them appears in the next morning's situation report.

• Linux — Linux

Patchlage reports hits and suspected hits. About everything else this system says nothing — neither this page nor the situation report ever claims that an estate is safe.