{"id":"CVE-2026-74739","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-74739","summary":"net/sched: cls_u32: skip hash tables in u32_bind_class()","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: cls_u32: skip hash tables in u32_bind_class()\n\nu32_walk() enumerates both struct tc_u_hnode and struct tc_u_knode\nthrough the walker callback. u32_bind_class() unconditionally casts the\npassed fh to tc_u_knode and accesses &n->res, so when fh is actually a\ntc_u_hnode, which has no tcf_result member, this results in a\nslab-out-of-bounds read of res->classid in tc_cls_bind_class().\n\nThe issue can be reproduced with the following commands:\n\n    tc qdisc add dev lo root handle 1: hfsc\n    tc class add dev lo parent 1: classid 1:1 hfsc sc rate 1000kbit\n    tc filter add dev lo parent 1:1 protocol ip prio 1 u32 match u32 0 0 flowid 1:1\n    tc class add dev lo parent 1: classid 1:2 hfsc sc rate 2000kbit\n\nFix this by skipping hash tables via the TC_U32_KEY(handle) check.","published":"2026-08-26T14:36:51.746Z","modified":"2026-08-28T03:47:16.144489291Z","cvss":{"score":7.8,"severity":"HIGH","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"},"epss":{"score":0.00138,"percentile":0.03523,"asOf":"2026-08-27"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Linux","name":"Kernel","fixedVersion":"6.1.184"}],"fix":null,"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/19d114b93c94bdef70496f26685c2a6b242f41b3"},{"type":"WEB","url":"https://git.kernel.org/stable/c/31f26a95eeee926946809ac456c61a3217936a62"},{"type":"WEB","url":"https://git.kernel.org/stable/c/594a064d603202b9ee21e07679d854e5c1750cc4"},{"type":"WEB","url":"https://git.kernel.org/stable/c/6d3724e616faf952c3adcf8414fc21a828ef3709"},{"type":"WEB","url":"https://git.kernel.org/stable/c/e71f8e9ed6f311410b14741f6012afe01869c0fa"},{"type":"WEB","url":"https://git.kernel.org/stable/c/ec5f3005586a785689fd568361b0c5925cb1548b"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/74xxx/CVE-2026-74739.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-74739"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-28T03:47:16.144489291Z"}}