{"id":"CVE-2026-98299","revision":"5cafaec48e154beeaa96097c24228c8d","records":[{"revision":"5cafaec48e154beeaa96097c24228c8d","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-98299","aliases":[],"title":"tcp: do not let tcp_rmem be set below 4096","description":"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.","state":0,"publishedAt":"2026-10-06T08:45:57.226+00:00","modifiedAt":"2026-10-19T09:17:10.154+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"unaffected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"Documentation/networking/ip-sysctl.rst\",\n                        \"net/ipv4/sysctl_net_ipv4.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\n                            \"lessThan\": \"879907631b9e70eedb62d76461b29afa106ebe7a\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\n                            \"lessThan\": \"8e32532d0fa3191ecf9524b0e6bafa0832e712ba\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\n                            \"lessThan\": \"67b83c15bed9eeeb8d1a6dbf88a5f79525970173\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\n                            \"lessThan\": \"9a4f49bf8d2da4e52e904f60c29cca317bab9b3a\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\n                            \"lessThan\": \"60df201dbb19a1bf6478b56d100f7ae1fe90e46a\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\n                            \"lessThan\": \"7898bda1ebc198f5559b301a96dd5398edd4d4d3\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\n                            \"lessThan\": \"1c4bb940c3bb4325bb88ac1b7eaf5faaa39e7d63\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"1da177e4c3f41524e886b7f1b8a0c1fc7321cac2\",\n                            \"lessThan\": \"83a945a529d6e002dd7339c532288a931f463dba\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        }\n                    ]\n                }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"affected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"Documentation/networking/ip-sysctl.rst\",\n                        \"net/ipv4/sysctl_net_ipv4.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"2.6.12\",\n                            \"status\": \"affected\"\n                        },\n                        {\n                            \"version\": \"0\",\n                            \"lessThan\": \"2.6.12\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"5.10.271\",\n                            \"lessThanOrEqual\": \"5.10.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"5.15.222\",\n                            \"lessThanOrEqual\": \"5.15.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.1.189\",\n                            \"lessThanOrEqual\": \"6.1.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.6.158\",\n                            \"lessThanOrEqual\": \"6.6.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.12.112\",\n                            \"lessThanOrEqual\": \"6.12.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.18.54\",\n                            \"lessThanOrEqual\": \"6.18.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.2.8\",\n                            \"lessThanOrEqual\": \"7.2.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.3\",\n                            \"lessThanOrEqual\": \"*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"original_commit_for_fix\"\n                        }\n                    ]\n                }"}],"metrics":[],"references":["https://git.kernel.org/stable/c/879907631b9e70eedb62d76461b29afa106ebe7a","https://git.kernel.org/stable/c/8e32532d0fa3191ecf9524b0e6bafa0832e712ba","https://git.kernel.org/stable/c/67b83c15bed9eeeb8d1a6dbf88a5f79525970173","https://git.kernel.org/stable/c/9a4f49bf8d2da4e52e904f60c29cca317bab9b3a","https://git.kernel.org/stable/c/60df201dbb19a1bf6478b56d100f7ae1fe90e46a","https://git.kernel.org/stable/c/7898bda1ebc198f5559b301a96dd5398edd4d4d3","https://git.kernel.org/stable/c/1c4bb940c3bb4325bb88ac1b7eaf5faaa39e7d63","https://git.kernel.org/stable/c/83a945a529d6e002dd7339c532288a931f463dba"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-98299","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-98299","identifiers":["CVE-2026-98299"]},"retained":false,"historicalAffected":[]}],"coverage":[]}