Answer in brief
CVE-2026-98299 records a Unknown severity vulnerability in tcp: do not let tcp_rmem be set below 4096. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Linux/Linuxgeneric | >=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <879907631b9e70eedb62d76461b29afa106ebe7a || >=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <8e32532d0fa3191ecf9524b0e6bafa0832e712ba || >=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <67b83c15bed9eeeb8d1a6dbf88a5f79525970173 || >=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <9a4f49bf8d2da4e52e904f60c29cca317bab9b3a || >=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <60df201dbb19a1bf6478b56d100f7ae1fe90e46a || >=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <7898bda1ebc198f5559b301a96dd5398edd4d4d3 || >=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <1c4bb940c3bb4325bb88ac1b7eaf5faaa39e7d63 || >=1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <83a945a529d6e002dd7339c532288a931f463dba | 879907631b9e70eedb62d76461b29afa106ebe7a, 8e32532d0fa3191ecf9524b0e6bafa0832e712ba, 67b83c15bed9eeeb8d1a6dbf88a5f79525970173, 9a4f49bf8d2da4e52e904f60c29cca317bab9b3a, 60df201dbb19a1bf6478b56d100f7ae1fe90e46a, 7898bda1ebc198f5559b301a96dd5398edd4d4d3, 1c4bb940c3bb4325bb88ac1b7eaf5faaa39e7d63, 83a945a529d6e002dd7339c532288a931f463dba |
| Linux/Linuxgeneric | 2.6.12 | Not reported |
Published upstream
Oct 6, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Oct 6, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Oct 6, 2026
In the Linux kernel, the following vulnerability has been resolved: tcp: do not let tcp_rmem be set below 4096 We can hit a division by zero crash in tcp_rcvbuf_grow() and tcp_rcv_space_adjust(): divide error: 0000 [#1] PREEMPT SMP RIP: 0010:tcp_rcvbuf_grow+0x187/0x450 net/ipv4/tcp_input.c:939 ... grow = div_u64(((u64)rcvwin << 1) * (newval - oldval), oldval); The division uses oldval = tp->rcvq_space.space as divisor. When tp->rcvq_space.space is zero, this leads to a divide-by-zero exception. tp->rcvq_space.space is initialized in tcp_init_buffer_space(): tp->rcvq_space.space = min3(tp->rcv_ssthresh, tp->rcv_wnd, (u32)TCP_INIT_CWND * tp->advmss); If tcp_rmem[1] is configured to very small values (such as 1), sk->sk_rcvbuf is initialized to 1. Then tcp_full_space(sk), which computes (sk->sk_rcvbuf * scaling_ratio) >> 8, truncates to 0. This sets tp->window_clamp = 0, tp->rcv_ssthresh = 0, and tp->rcvq_space.space = 0. Later, when data arrives and DRS is invoked, tcp_rcvbuf_grow() divides by oldval == 0. Back in 2015, commit b1cb59cf2efe ("net: sysctl_net_core: check SNDBUF and RCVBUF for min length") ensured that net.core.rmem_default and net.core.rmem_max cannot be set below SOCK_MIN_RCVBUF. Similarly, SO_RCVBUF setsockopt enforces max_t(int, val * 2, SOCK_MIN_RCVBUF). However, net.ipv4.tcp_rmem still had .extra1 = SYSCTL_ONE, allowing arbitrarily small values. Because SOCK_MIN_RCVBUF depends on sizeof(struct sk_buff) and cacheline alignment, its value varies across architectures and configuration options. Using a fixed constant of 4096 ensures a predictable, architecture- independent lower bound that is safely above SOCK_MIN_RCVBUF everywhere and matches the documented 4K default. Fix this by setting tcp_rmem.extra1 to 4096 and updating the documentation.
Quoted source text, attributed separately from HOL analysis.