{"id":"CVE-2026-74620","summary":"net/sched: act_gact, act_police: range check the fallback control action","details":"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 \u003e 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 \u003e= 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.","modified":"2026-08-25T03:30:28.597361298Z","published":"2026-08-22T15:32:04.254Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/74xxx/CVE-2026-74620.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/2e8df8c9190335475a3b64a159d3efd8cdd1cb73"},{"type":"WEB","url":"https://git.kernel.org/stable/c/5344e01179baa37547ab29fd7b8614f83faa190c"},{"type":"WEB","url":"https://git.kernel.org/stable/c/5f038affdacaffedf6a85a06cf59ec0a852d36a7"},{"type":"WEB","url":"https://git.kernel.org/stable/c/6bcb8839aa2d686964a4154650afc4db91e1c514"},{"type":"WEB","url":"https://git.kernel.org/stable/c/725efc2ab4a40affc4e285a2dc4896d103948a6c"},{"type":"WEB","url":"https://git.kernel.org/stable/c/883b56ae58fe657d8497806c7059646e9ba6dbd0"},{"type":"WEB","url":"https://git.kernel.org/stable/c/92f00f1d4d204a428b38e26fce3baee144b6955d"},{"type":"WEB","url":"https://git.kernel.org/stable/c/efa58aeb6a99028b1fbc3ab2f31ba3a881211ad4"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/74xxx/CVE-2026-74620.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-74620"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"720f22fed81bc6fd1765db7014651b6718887bea"},{"fixed":"5f038affdacaffedf6a85a06cf59ec0a852d36a7"},{"fixed":"efa58aeb6a99028b1fbc3ab2f31ba3a881211ad4"},{"fixed":"725efc2ab4a40affc4e285a2dc4896d103948a6c"},{"fixed":"6bcb8839aa2d686964a4154650afc4db91e1c514"},{"fixed":"5344e01179baa37547ab29fd7b8614f83faa190c"},{"fixed":"92f00f1d4d204a428b38e26fce3baee144b6955d"},{"fixed":"2e8df8c9190335475a3b64a159d3efd8cdd1cb73"},{"fixed":"883b56ae58fe657d8497806c7059646e9ba6dbd0"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-74620.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"5.3.0"},{"fixed":"5.10.266"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.11.0"},{"fixed":"5.15.216"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.183"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.152"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.104"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.45"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.1.9"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-74620.json"}}],"schema_version":"1.9.0"}