{"id":"CVE-2026-74620","state":"PUBLISHED","title":"net/sched: act_gact, act_police: range check the fallback control action","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: act_gact, act_police: range check the fallback control action\n\ntcf_action_check_ctrlact() range checks the primary control action:\n\n\tif (!opcode)\n\t\tret = action > TC_ACT_VALUE_MAX ? -EINVAL : 0;\n\nTC_ACT_VALUE_MAX is TC_ACT_TRAP, so kernel-internal verdicts above it\ncannot be set that way. But act_gact and act_police each carry a second,\nindependent control action supplied by user space that never reaches that\nhelper - TCA_GACT_PROB.paction and TCA_POLICE_RESULT. Both only reject\nTC_ACT_GOTO_CHAIN, so any other value is stored verbatim and returned\nverbatim from the action.\n\nIn particular user space can store TC_ACT_CONSUMED, which is\nTC_ACT_VALUE_MAX + 1 and is deliberately not part of the UAPI value\nrange. That verdict tells every caller the action took ownership of the\nskb, so nobody frees it: sch_handle_ingress(), sch_handle_egress() and\ntcf_qevent_handle() all deliberately skip the free for it. The result is\none leaked sk_buff plus its data buffer per packet traversing the filter,\nunbounded, for all traffic on the chain including kernel-generated\npackets.\n\nBoth are trivially deterministic. act_gact clamps tcfg_pval to >= 1, so\nwith pval = 1 gact_determ() returns the fallback for every packet.\nact_police has no mandatory rate, so rate = 0 leaves tcfp_mtu = ~0 and\ntcf_police_mtu_check() always passes.\n\nTC_ACT_CONSUMED was added by commit 720f22fed81b (\"net: sched: refactor\nreinsert action\"), after both goto-chain guards were written:\ncommit 9469f375ab09 (\"net/sched: act_gact: disallow 'goto chain' on\nfallback control action\") and\ncommit c08f5ed5d625 (\"net/sched: act_police: disallow 'goto chain' on\nfallback control action\"). Neither guard was widened when the new\nverdict appeared.\n\nFactor the existing range test out of tcf_action_check_ctrlact() as\ntcf_action_valid() and apply it to both fallbacks. The helper cannot call\ntcf_action_check_ctrlact() directly because that also allocates a\ngoto_chain, which is exactly what these two sites must not do.\n\nReproduced on v7.2-rc6: kmemleak reports one leaked 232-byte\nskbuff_head_cache object plus its 704-byte data buffer per packet. With\nthis patch both configurations are rejected with -EINVAL and kmemleak\nreports none.","publishedAt":"2026-08-22T15:32:04.254Z","updatedAt":"2026-08-23T12:47:46.379Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"720f22fed81bc6fd1765db7014651b6718887bea","status":"affected","lessThan":"5f038affdacaffedf6a85a06cf59ec0a852d36a7","versionType":"git"},{"version":"720f22fed81bc6fd1765db7014651b6718887bea","status":"affected","lessThan":"efa58aeb6a99028b1fbc3ab2f31ba3a881211ad4","versionType":"git"},{"version":"720f22fed81bc6fd1765db7014651b6718887bea","status":"affected","lessThan":"725efc2ab4a40affc4e285a2dc4896d103948a6c","versionType":"git"},{"version":"720f22fed81bc6fd1765db7014651b6718887bea","status":"affected","lessThan":"6bcb8839aa2d686964a4154650afc4db91e1c514","versionType":"git"},{"version":"720f22fed81bc6fd1765db7014651b6718887bea","status":"affected","lessThan":"5344e01179baa37547ab29fd7b8614f83faa190c","versionType":"git"},{"version":"720f22fed81bc6fd1765db7014651b6718887bea","status":"affected","lessThan":"92f00f1d4d204a428b38e26fce3baee144b6955d","versionType":"git"},{"version":"720f22fed81bc6fd1765db7014651b6718887bea","status":"affected","lessThan":"2e8df8c9190335475a3b64a159d3efd8cdd1cb73","versionType":"git"},{"version":"720f22fed81bc6fd1765db7014651b6718887bea","status":"affected","lessThan":"883b56ae58fe657d8497806c7059646e9ba6dbd0","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/net/act_api.h","net/sched/act_gact.c","net/sched/act_police.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.3","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.3","versionType":"semver"},{"version":"5.10.266","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.216","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.183","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.152","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.104","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.45","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.9","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/net/act_api.h","net/sched/act_gact.c","net/sched/act_police.c"]}],"references":["https://git.kernel.org/stable/c/5f038affdacaffedf6a85a06cf59ec0a852d36a7","https://git.kernel.org/stable/c/efa58aeb6a99028b1fbc3ab2f31ba3a881211ad4","https://git.kernel.org/stable/c/725efc2ab4a40affc4e285a2dc4896d103948a6c","https://git.kernel.org/stable/c/6bcb8839aa2d686964a4154650afc4db91e1c514","https://git.kernel.org/stable/c/5344e01179baa37547ab29fd7b8614f83faa190c","https://git.kernel.org/stable/c/92f00f1d4d204a428b38e26fce3baee144b6955d","https://git.kernel.org/stable/c/2e8df8c9190335475a3b64a159d3efd8cdd1cb73","https://git.kernel.org/stable/c/883b56ae58fe657d8497806c7059646e9ba6dbd0"],"weaknesses":[],"ingestedAt":"2026-10-29T20:12:58.252Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/74xxx/CVE-2026-74620.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-74620","state":"PUBLISHED","datePublished":"2026-08-22T15:32:04.254Z","dateUpdated":"2026-08-23T12:47:46.379Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-08-15T05:44:03.921Z"},"containers":{"cna":{"title":"net/sched: act_gact, act_police: range check the fallback control action","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: act_gact, act_police: range check the fallback control action\n\ntcf_action_check_ctrlact() range checks the primary control action:\n\n\tif (!opcode)\n\t\tret = action > TC_ACT_VALUE_MAX ? -EINVAL : 0;\n\nTC_ACT_VALUE_MAX is TC_ACT_TRAP, so kernel-internal verdicts above it\ncannot be set that way. But act_gact and act_police each carry a second,\nindependent control action supplied by user space that never reaches that\nhelper - TCA_GACT_PROB.paction and TCA_POLICE_RESULT. Both only reject\nTC_ACT_GOTO_CHAIN, so any other value is stored verbatim and returned\nverbatim from the action.\n\nIn particular user space can store TC_ACT_CONSUMED, which is\nTC_ACT_VALUE_MAX + 1 and is deliberately not part of the UAPI value\nrange. That verdict tells every caller the action took ownership of the\nskb, so nobody frees it: sch_handle_ingress(), sch_handle_egress() and\ntcf_qevent_handle() all deliberately skip the free for it. The result is\none leaked sk_buff plus its data buffer per packet traversing the filter,\nunbounded, for all traffic on the chain including kernel-generated\npackets.\n\nBoth are trivially deterministic. act_gact clamps tcfg_pval to >= 1, so\nwith pval = 1 gact_determ() returns the fallback for every packet.\nact_police has no mandatory rate, so rate = 0 leaves tcfp_mtu = ~0 and\ntcf_police_mtu_check() always passes.\n\nTC_ACT_CONSUMED was added by commit 720f22fed81b (\"net: sched: refactor\nreinsert action\"), after both goto-chain guards were written:\ncommit 9469f375ab09 (\"net/sched: act_gact: disallow 'goto chain' on\nfallback control action\") and\ncommit c08f5ed5d625 (\"net/sched: act_police: disallow 'goto chain' on\nfallback control action\"). Neither guard was widened when the new\nverdict appeared.\n\nFactor the existing range test out of tcf_action_check_ctrlact() as\ntcf_action_valid() and apply it to both fallbacks. The helper cannot call\ntcf_action_check_ctrlact() directly because that also allocates a\ngoto_chain, which is exactly what these two sites must not do.\n\nReproduced on v7.2-rc6: kmemleak reports one leaked 232-byte\nskbuff_head_cache object plus its 704-byte data buffer per packet. With\nthis patch both configurations are rejected with -EINVAL and kmemleak\nreports none."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"720f22fed81bc6fd1765db7014651b6718887bea","status":"affected","lessThan":"5f038affdacaffedf6a85a06cf59ec0a852d36a7","versionType":"git"},{"version":"720f22fed81bc6fd1765db7014651b6718887bea","status":"affected","lessThan":"efa58aeb6a99028b1fbc3ab2f31ba3a881211ad4","versionType":"git"},{"version":"720f22fed81bc6fd1765db7014651b6718887bea","status":"affected","lessThan":"725efc2ab4a40affc4e285a2dc4896d103948a6c","versionType":"git"},{"version":"720f22fed81bc6fd1765db7014651b6718887bea","status":"affected","lessThan":"6bcb8839aa2d686964a4154650afc4db91e1c514","versionType":"git"},{"version":"720f22fed81bc6fd1765db7014651b6718887bea","status":"affected","lessThan":"5344e01179baa37547ab29fd7b8614f83faa190c","versionType":"git"},{"version":"720f22fed81bc6fd1765db7014651b6718887bea","status":"affected","lessThan":"92f00f1d4d204a428b38e26fce3baee144b6955d","versionType":"git"},{"version":"720f22fed81bc6fd1765db7014651b6718887bea","status":"affected","lessThan":"2e8df8c9190335475a3b64a159d3efd8cdd1cb73","versionType":"git"},{"version":"720f22fed81bc6fd1765db7014651b6718887bea","status":"affected","lessThan":"883b56ae58fe657d8497806c7059646e9ba6dbd0","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/net/act_api.h","net/sched/act_gact.c","net/sched/act_police.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.3","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.3","versionType":"semver"},{"version":"5.10.266","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.216","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.183","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.152","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.104","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.45","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.9","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["include/net/act_api.h","net/sched/act_gact.c","net/sched/act_police.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/5f038affdacaffedf6a85a06cf59ec0a852d36a7"},{"url":"https://git.kernel.org/stable/c/efa58aeb6a99028b1fbc3ab2f31ba3a881211ad4"},{"url":"https://git.kernel.org/stable/c/725efc2ab4a40affc4e285a2dc4896d103948a6c"},{"url":"https://git.kernel.org/stable/c/6bcb8839aa2d686964a4154650afc4db91e1c514"},{"url":"https://git.kernel.org/stable/c/5344e01179baa37547ab29fd7b8614f83faa190c"},{"url":"https://git.kernel.org/stable/c/92f00f1d4d204a428b38e26fce3baee144b6955d"},{"url":"https://git.kernel.org/stable/c/2e8df8c9190335475a3b64a159d3efd8cdd1cb73"},{"url":"https://git.kernel.org/stable/c/883b56ae58fe657d8497806c7059646e9ba6dbd0"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-23T12:47:46.379Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.3","versionEndExcluding":"5.10.266"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.3","versionEndExcluding":"5.15.216"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.3","versionEndExcluding":"6.1.183"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.3","versionEndExcluding":"6.6.152"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.3","versionEndExcluding":"6.12.104"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.3","versionEndExcluding":"6.18.45"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.3","versionEndExcluding":"7.1.9"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.3","versionEndExcluding":"7.2"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}