{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-98299","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-09-25T10:25:14.337Z","datePublished":"2026-10-06T08:45:57.226Z","dateUpdated":"2026-10-06T08:45:57.226Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-10-06T08:45:57.226Z"},"descriptions":[{"lang":"en","value":"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."}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["Documentation/networking/ip-sysctl.rst","net/ipv4/sysctl_net_ipv4.c"],"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"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["Documentation/networking/ip-sysctl.rst","net/ipv4/sysctl_net_ipv4.c"],"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-rc4","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12","versionEndExcluding":"5.10.271"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12","versionEndExcluding":"5.15.222"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12","versionEndExcluding":"6.1.189"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12","versionEndExcluding":"6.6.158"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12","versionEndExcluding":"6.12.112"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12","versionEndExcluding":"6.18.54"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12","versionEndExcluding":"7.2.8"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.12","versionEndExcluding":"7.3-rc4"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/879907631b9e70eedb62d76461b29afa106ebe7a"},{"url":"https://git.kernel.org/stable/c/8e32532d0fa3191ecf9524b0e6bafa0832e712ba"},{"url":"https://git.kernel.org/stable/c/67b83c15bed9eeeb8d1a6dbf88a5f79525970173"},{"url":"https://git.kernel.org/stable/c/9a4f49bf8d2da4e52e904f60c29cca317bab9b3a"},{"url":"https://git.kernel.org/stable/c/60df201dbb19a1bf6478b56d100f7ae1fe90e46a"},{"url":"https://git.kernel.org/stable/c/7898bda1ebc198f5559b301a96dd5398edd4d4d3"},{"url":"https://git.kernel.org/stable/c/1c4bb940c3bb4325bb88ac1b7eaf5faaa39e7d63"},{"url":"https://git.kernel.org/stable/c/83a945a529d6e002dd7339c532288a931f463dba"}],"title":"tcp: do not let tcp_rmem be set below 4096","x_generator":{"engine":"bippy-1.2.0"}}}}