{"id":"CVE-2026-98643","summary":"bpf: Fix out-of-bounds read of rtt_min in sock_ops","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fix out-of-bounds read of rtt_min in sock_ops\n\nA sockops prog reading skops-\u003ertt_min never checks the sk type: on the\ntcp_conn_request() path sock_ops-\u003esk is a request_sock (non-full), and the\nctx rewrite casts it to a tcp_sock (full) and reads rtt_min past the end of\nthe request_sock, returning dirty adjacent memory.\n\n\tSEC(\"sockops\")\n\tint prog(struct bpf_sock_ops *skops)\n\t{\n\t\tswitch (skops-\u003eop) {\n\t\tcase BPF_SOCK_OPS_RWND_INIT:\n\t\t\tleak = skops-\u003ertt_min;   /* reads the request_sock OOB */\n\t\t...\n\t\t}\n\t}\n\nFor instance one such read returned rtt_min=0xffff8881, the high half of a\nleaked kernel pointer.\n\nGuarding that cast is exactly what SOCK_OPS_GET_FIELD() does -- it checks\nis_locked_tcp_sock and returns 0 when sock_ops-\u003esk is not a locked full\nsocket. Every other tcp_sock field in sock_ops goes through it; rtt_min is\nthe only one open-coded, so it skips the check.\n\nRead rtt_min through SOCK_OPS_GET_FIELD() too. rtt_min is a bit special:\nit is a struct minmax and we only want the current min, so pass\nrtt_min.s[0].v. That is equivalent to the old hand-computed offset\n\n\toffsetof(struct tcp_sock, rtt_min) + sizeof_field(struct minmax_sample, t)\n\n(s[0] sits at rtt_min + 0 and .v at + sizeof(.t), i.e. what minmax_get()\nreturns), so the loaded field is unchanged and only the full-sock guard is\nadded. The two BUILD_BUG_ON()s that protected the hand-computed offset\nare no longer needed.\n\nBefore patch:\n\n\t0: r1 = *(u64 *)(r1 +0)      ; r1 = skops-\u003esk\n\t1: r1 = *(u32 *)(r1 +2324)   ; ((tcp_sock *)sk)-\u003ertt_min.s[0].v\n\nAfter patch:\n\n\t0: *(u64 *)(r1 +56) = r9\n\t1: r9 = *(u8 *)(r1 +50)      ; is_locked_tcp_sock\n\t2: if r9 == 0 goto pc+4      ; not a locked full sock -\u003e 0\n\t3: r9 = *(u64 *)(r1 +56)\n\t4: r1 = *(u64 *)(r1 +0)      ; r1 = skops-\u003esk\n\t5: r1 = *(u32 *)(r1 +2324)   ; rtt_min.s[0].v\n\t6: goto pc+2\n\t7: r9 = *(u64 *)(r1 +56)\n\t8: r1 = 0","modified":"2026-10-20T02:30:43.821441914Z","published":"2026-10-18T15:20:14.561Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98643.json"},"references":[{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"},{"type":"WEB","url":"https://git.kernel.org/stable/c/0c796efa919f52f788c22c79d1f1b70321696b3d"},{"type":"WEB","url":"https://git.kernel.org/stable/c/3a46f14e6cf375f3ca38f8f6e6524749e24ea0a8"},{"type":"WEB","url":"https://git.kernel.org/stable/c/6785313d4fac96afb21ef193610c1fa88b1a9e64"},{"type":"WEB","url":"https://git.kernel.org/stable/c/75f8cf22463d82bb1fb0239a3d485fc8f4c8ef03"},{"type":"WEB","url":"https://git.kernel.org/stable/c/a8a9becbac93a9f54f4d565f1f3005eb08a7912f"},{"type":"WEB","url":"https://git.kernel.org/stable/c/cba54d142c43ec96d8c4d566f66439e8c0afded7"},{"type":"WEB","url":"https://git.kernel.org/stable/c/fc9d0e6e9d86fbefe7b8fe6ee49f4cf102add79d"},{"type":"WEB","url":"https://git.kernel.org/stable/c/fd6bf2721933d8c90bc4ce57f3e204c9295e7e3f"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98643.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98643"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"44f0e43037d3a17b043843ba67610ac7c7e37db6"},{"fixed":"0c796efa919f52f788c22c79d1f1b70321696b3d"},{"fixed":"fc9d0e6e9d86fbefe7b8fe6ee49f4cf102add79d"},{"fixed":"fd6bf2721933d8c90bc4ce57f3e204c9295e7e3f"},{"fixed":"a8a9becbac93a9f54f4d565f1f3005eb08a7912f"},{"fixed":"3a46f14e6cf375f3ca38f8f6e6524749e24ea0a8"},{"fixed":"6785313d4fac96afb21ef193610c1fa88b1a9e64"},{"fixed":"cba54d142c43ec96d8c4d566f66439e8c0afded7"},{"fixed":"75f8cf22463d82bb1fb0239a3d485fc8f4c8ef03"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98643.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"4.16.0"},{"fixed":"5.10.271"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.11.0"},{"fixed":"5.15.222"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.189"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.158"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.112"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.55"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.2.9"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98643.json"}}],"schema_version":"1.9.0"}