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CVE PROGRAM SOURCE RECORD7.5 High

CVE-2026-74621

net/sched: act_ct: fix sk_buff leak when the header checks reject a packet

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Status
Published
Published
Updated
Assigning organization
Linux

Description

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.

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Linux Linux

Default version status: unaffected

  • 172ba7d46c202e679f3ccb10264c67416aaeb1c4 to < b5dbecc2016e1692fd1c2532af9c41ba729cb747affected
  • 0b5b831122fc3789fff75be433ba3e4dd7b779d4 to < 23e97d594ddd0153020c506d5041048fbde1beb4affected
  • 73f7da5fd124f2cda9161e2e46114915e6e82e97 to < 737873a59905a54ca0d2d127ef882f3f88bf4379affected
  • 3f14b377d01d8357eba032b4cabc8c1149b458b6 to < 47d99828591d0fe8be4b9c8992ff3b8e47968db9affected
  • 3f14b377d01d8357eba032b4cabc8c1149b458b6 to < b47bb899e04b5407c5a63fe88d4b6676586a6e84affected
  • 3f14b377d01d8357eba032b4cabc8c1149b458b6 to < 439d3e404f9d5e515911cc8132cde198b337c19eaffected
  • 3f14b377d01d8357eba032b4cabc8c1149b458b6 to < 8a7ed561671aa6a911a2de99e59ef670a4d0b1dfaffected
  • f5346df0591d10bc948761ca854b1fae6d2ef441affected
  • 5.15.148 to < 5.15.217affected
  • 6.1.75 to < 6.1.184affected
  • 6.6.14 to < 6.6.152affected
  • 6.7.2 to < 6.8affected

Linux Linux

Default version status: affected

  • 6.8affected
  • 0 to < 6.8unaffected
  • 5.15.217 to ≤ 5.15.*unaffected
  • 6.1.184 to ≤ 6.1.*unaffected
  • 6.6.152 to ≤ 6.6.*unaffected
  • 6.12.104 to ≤ 6.12.*unaffected
  • 6.18.45 to ≤ 6.18.*unaffected
  • 7.1.9 to ≤ 7.1.*unaffected
  • 7.2 to ≤ *unaffected

References