{"schema":"threatline.record/2","record":{"id":"CVE-2026-98299","aliases":[],"summary":"tcp: do not let tcp_rmem be set below 4096","details":"In the Linux kernel, the following vulnerability has been resolved:\n\ntcp: do not let tcp_rmem be set below 4096\n\nWe can hit a division by zero crash in tcp_rcvbuf_grow()\nand tcp_rcv_space_adjust():\n\ndivide error: 0000 [#1] PREEMPT SMP\nRIP: 0010:tcp_rcvbuf_grow+0x187/0x450 net/ipv4/tcp_input.c:939\n...\ngrow = div_u64(((u64)rcvwin << 1) * (newval - oldval), oldval);\n\nThe division uses oldval = tp->rcvq_space.space as divisor.\nWhen tp->rcvq_space.space is zero, this leads to a divide-by-zero\nexception.\n\ntp->rcvq_space.space is initialized in tcp_init_buffer_space():\n    tp->rcvq_space.space = min3(tp->rcv_ssthresh, tp->rcv_wnd,\n                                (u32)TCP_INIT_CWND * tp->advmss);\n\nIf tcp_rmem[1] is configured to very small values (such as 1),\nsk->sk_rcvbuf is initialized to 1. Then tcp_full_space(sk), which\ncomputes (sk->sk_rcvbuf * scaling_ratio) >> 8, truncates to 0.\nThis sets tp->window_clamp = 0, tp->rcv_ssthresh = 0, and\ntp->rcvq_space.space = 0. Later, when data arrives and DRS is invoked,\ntcp_rcvbuf_grow() divides by oldval == 0.\n\nBack in 2015, commit b1cb59cf2efe (\"net: sysctl_net_core: check SNDBUF\nand RCVBUF for min length\") ensured that net.core.rmem_default and\nnet.core.rmem_max cannot be set below SOCK_MIN_RCVBUF. Similarly,\nSO_RCVBUF setsockopt enforces max_t(int, val * 2, SOCK_MIN_RCVBUF).\n\nHowever, net.ipv4.tcp_rmem still had .extra1 = SYSCTL_ONE, allowing\narbitrarily small values.\n\nBecause SOCK_MIN_RCVBUF depends on sizeof(struct sk_buff) and cacheline\nalignment, its value varies across architectures and configuration options.\nUsing a fixed constant of 4096 ensures a predictable, architecture-\nindependent lower bound that is safely above SOCK_MIN_RCVBUF everywhere\nand matches the documented 4K default.\n\nFix this by setting tcp_rmem.extra1 to 4096 and updating the documentation.","categories":["Operating systems"],"product":"Linux","vendor":"Linux","ecosystem":null,"affected_ranges":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98299","source_modified_at":"2026-10-19T09:17:10.154Z","fetched_at":"2026-10-23T18:45:31.882637Z","product":"Linux","vendor":"Linux","versions":[{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","lessThan":"879907631b9e70eedb62d76461b29afa106ebe7a","status":"affected","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","lessThan":"8e32532d0fa3191ecf9524b0e6bafa0832e712ba","status":"affected","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","lessThan":"67b83c15bed9eeeb8d1a6dbf88a5f79525970173","status":"affected","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","lessThan":"9a4f49bf8d2da4e52e904f60c29cca317bab9b3a","status":"affected","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","lessThan":"60df201dbb19a1bf6478b56d100f7ae1fe90e46a","status":"affected","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","lessThan":"7898bda1ebc198f5559b301a96dd5398edd4d4d3","status":"affected","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","lessThan":"1c4bb940c3bb4325bb88ac1b7eaf5faaa39e7d63","status":"affected","versionType":"git"},{"version":"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2","lessThan":"83a945a529d6e002dd7339c532288a931f463dba","status":"affected","versionType":"git"}],"defaultStatus":"unaffected"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98299","source_modified_at":"2026-10-19T09:17:10.154Z","fetched_at":"2026-10-23T18:45:31.882637Z","product":"Linux","vendor":"Linux","versions":[{"version":"2.6.12","status":"affected"},{"version":"0","lessThan":"2.6.12","status":"unaffected","versionType":"semver"},{"version":"5.10.271","lessThanOrEqual":"5.10.*","status":"unaffected","versionType":"semver"},{"version":"5.15.222","lessThanOrEqual":"5.15.*","status":"unaffected","versionType":"semver"},{"version":"6.1.189","lessThanOrEqual":"6.1.*","status":"unaffected","versionType":"semver"},{"version":"6.6.158","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.112","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.54","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.2.8","lessThanOrEqual":"7.2.*","status":"unaffected","versionType":"semver"},{"version":"7.3","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}],"defaultStatus":"affected"}],"fixed_versions":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98299","source_modified_at":"2026-10-19T09:17:10.154Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"879907631b9e70eedb62d76461b29afa106ebe7a","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98299","source_modified_at":"2026-10-19T09:17:10.154Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"8e32532d0fa3191ecf9524b0e6bafa0832e712ba","basis":"first unaffected version stated in the CVE record"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98299","source_modified_at":"2026-10-19T09:17:10.154Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"67b83c15bed9eeeb8d1a6dbf88a5f79525970173","basis":"first unaffected version stated in the CVE record"},{"source":"CVE 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List","url":"https://www.cve.org/CVERecord?id=CVE-2026-98299","fetched_at":"2026-10-23T18:45:31.882637Z","source_modified_at":"2026-10-19T09:17:10.154Z"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-98299","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-23"}],"sources":["CVE List","EPSS"],"references":[{"source":"CVE List","url":"https://git.kernel.org/stable/c/879907631b9e70eedb62d76461b29afa106ebe7a"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/8e32532d0fa3191ecf9524b0e6bafa0832e712ba"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/67b83c15bed9eeeb8d1a6dbf88a5f79525970173"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/9a4f49bf8d2da4e52e904f60c29cca317bab9b3a"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/60df201dbb19a1bf6478b56d100f7ae1fe90e46a"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/7898bda1ebc198f5559b301a96dd5398edd4d4d3"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/1c4bb940c3bb4325bb88ac1b7eaf5faaa39e7d63"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/83a945a529d6e002dd7339c532288a931f463dba"}],"locations":[],"motoko_assessment":{"status":"requires_architecture_review","automatic_remediation":false},"cve_state":"PUBLISHED","classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":"product","confidence":"heuristic","reviewed":false},"change_timestamp":"2026-10-19T09:17:10.154Z","content_hash":"b813a73d04ff9762b286926c3b793482dd19dc170a948da82c4174eadcd87c0c"}}