CVE-2026-98299tcp: do not let tcp_rmem be set below 4096
- —Not scoredno CVSS score yet
- 0.18%Exploitation in 30 daysEPSS · top 93% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
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.
Timeline
ID reserved
By Linux
- 11 days later
· 11 days later
Published
- 13 days later
· 13 days later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
No CVSS score yet: neither the CNA, CISA nor NVD has scored this CVE. NVD status: Received.
- EPSS (exploitation in 30 days)
- 0.18% · top 93% of all CVEs (14 Nov 2026)
The list uses the assigner's score when there is one, then CISA's, then NVD's: Not scored.
Affected products
- affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 – < 879907631b9e70eedb62d76461b29afa106ebe7a
- affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 – < 8e32532d0fa3191ecf9524b0e6bafa0832e712ba
- affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 – < 67b83c15bed9eeeb8d1a6dbf88a5f79525970173
- affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 – < 9a4f49bf8d2da4e52e904f60c29cca317bab9b3a
- affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 – < 60df201dbb19a1bf6478b56d100f7ae1fe90e46a
- affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 – < 7898bda1ebc198f5559b301a96dd5398edd4d4d3
- affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 – < 1c4bb940c3bb4325bb88ac1b7eaf5faaa39e7d63
- affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 – < 83a945a529d6e002dd7339c532288a931f463dba
- affected 2.6.12
- unaffected < 2.6.12
- unaffected 5.10.271 – ≤ 5.10.*
- unaffected 5.15.222 – ≤ 5.15.*
- unaffected 6.1.189 – ≤ 6.1.*
- unaffected 6.6.158 – ≤ 6.6.*
- unaffected 6.12.112 – ≤ 6.12.*
- unaffected 6.18.54 – ≤ 6.18.*
- unaffected 7.2.8 – ≤ 7.2.*
- unaffected 7.3 – ≤ *
References
References8
- https://git.kernel.org/stable/c/879907631b9e70eedb62d76461b29afa106ebe7a (opens in a new tab)
- https://git.kernel.org/stable/c/8e32532d0fa3191ecf9524b0e6bafa0832e712ba (opens in a new tab)
- https://git.kernel.org/stable/c/67b83c15bed9eeeb8d1a6dbf88a5f79525970173 (opens in a new tab)
- https://git.kernel.org/stable/c/9a4f49bf8d2da4e52e904f60c29cca317bab9b3a (opens in a new tab)
- https://git.kernel.org/stable/c/60df201dbb19a1bf6478b56d100f7ae1fe90e46a (opens in a new tab)
- https://git.kernel.org/stable/c/7898bda1ebc198f5559b301a96dd5398edd4d4d3 (opens in a new tab)
- https://git.kernel.org/stable/c/1c4bb940c3bb4325bb88ac1b7eaf5faaa39e7d63 (opens in a new tab)
- https://git.kernel.org/stable/c/83a945a529d6e002dd7339c532288a931f463dba (opens in a new tab)
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-93284 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
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[](https://cveledger.app/cve/CVE-2026-98299)Record last updated .