CVE-2026-98299— tcp: do not let tcp_rmem be set below 4096
Quick assessment
Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.
在 Linux 内核中，已修复以下漏洞： tcp：禁止将 tcp_rmem 设置为低于 4096 的值 当 和 中发生除以零错误时，会导致崩溃： 该除法运算使用 作为除数。当 为零时，会引发除以零异常。 在 中初始化： 如果 被配置为非常小的值（例如 1），则 初始化为 1。此时， 计算表达式 ，结果截断为 0。这会导致 、 以及 。随后，当数据到达并触发 DRS（Dynamic Receive Scaling）时， 会对 进行除法运算，从而引发崩溃。 早在 2015 年，提交 （“net: sysctl_net_
Possible ATT&CK Techniques 1 AI
T1496 · Resource HijackingAffected Version Matrix 18
| Vendor | Product | Version Range | Status |
|---|---|---|---|
| Linux | Linux | 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 879907631b9e70eedb62d76461b29afa106ebe7a |
affected |
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 8e32532d0fa3191ecf9524b0e6bafa0832e712ba |
affected | ||
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 67b83c15bed9eeeb8d1a6dbf88a5f79525970173 |
affected | ||
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 9a4f49bf8d2da4e52e904f60c29cca317bab9b3a |
affected | ||
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 60df201dbb19a1bf6478b56d100f7ae1fe90e46a |
affected | ||
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 7898bda1ebc198f5559b301a96dd5398edd4d4d3 |
affected | ||
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 1c4bb940c3bb4325bb88ac1b7eaf5faaa39e7d63 |
affected | ||
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 83a945a529d6e002dd7339c532288a931f463dba |
affected | ||
| … +10 more rows | |||
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I. Basic Information for CVE-2026-98299
Vulnerability Information
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Vulnerability Title
tcp: do not let tcp_rmem be set below 4096
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Affected Products
II. Public POCs for CVE-2026-98299
| # | POC Description | Source Link | Shenlong Link |
|---|
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Patches & Fixes for CVE-2026-98299 (7)
Same Patch Batch · Linux · 2026-10-06 · 208 CVEs total
| CVE-2026-98323 | 9.8 CRITICAL | RDMA/siw: Bound fragmented header copies by the remaining length |
| CVE-2026-98365 | 9.8 CRITICAL | RDMA/rxe: Fix integer overflow in mr_check_range() leading to OOB access |
| CVE-2026-98282 | 8.8 HIGH | powerpc/iommu: Fix the overflow validation in iommu_tce_check_ioba |
| CVE-2026-98283 | 8.8 HIGH | KVM: PPC: Book3S HV: fix use-after-free in kvmhv_emulate_tlbie_all_lpid() |
| CVE-2026-98339 | 8.8 HIGH | wifi: cfg80211: don't filter by BSS type when removing stale entries |
| CVE-2026-98171 | 8.8 HIGH | smb: client: fix next_buffer UAF and NextCommand bounds in compound PDUs |
| CVE-2026-98261 | 8.1 HIGH | cifs: Fix server use-after-free in cifs_chan_skip_or_disable() |
| CVE-2026-98357 | 8.1 HIGH | IB/isert: wait for deferred control PDU completions before releasing the connection |
| CVE-2026-98239 | 8.1 HIGH | net: lan743x: fix RX checksum use-after-free |
| CVE-2026-98305 | 7.8 HIGH | net: dsa: mxl862xx: disable the stats poll on teardown |
| CVE-2026-98341 | 7.8 HIGH | wifi: cfg80211: don't free driver-owned scan requests |
| CVE-2026-98320 | 7.8 HIGH | netfilter: flowtable: hold reference on ct until flow is released |
| CVE-2026-98228 | 7.8 HIGH | mips: select CONFIG_WEAK_REORDERING_BEYOND_LLSC from CONFIG_EYEQ |
| CVE-2026-98229 | 7.8 HIGH | xfrm: save input state data before secpath resets |
| CVE-2026-98318 | 7.8 HIGH | smb: client: validate absolute native symlink targets before NT fixups |
| CVE-2026-98315 | 7.8 HIGH | ntfs: protect runlist updates with the runlist lock |
| CVE-2026-98260 | 7.8 HIGH | exec: Cleanup POSIX timers right after de_thread() |
| CVE-2026-98256 | 7.8 HIGH | signal: Prevent exec() race |
| CVE-2026-98258 | 7.8 HIGH | posix-cpu-timers: Prevent freeing a timer which is queued on the expiry list |
| CVE-2026-98254 | 7.8 HIGH | swiotlb: use the adjusted address for the highmem page lookup |
Showing top 20 of 208 CVEs. View all on vendor page → →
IV. Related Vulnerabilities
Same product: Linux
-
CVE-2026-98384
bpf: Fix out-of-bounds read of sk_protocol in bpf_sock_destr -
CVE-2026-98383
bpf: Disallow bpf_skb_pull_data() for LWT_SEG6LOCAL -
CVE-2026-98382
bpf: Reject dev-bound-only programs on other devices -
CVE-2026-98381
veth: manage XDP program pointers during channel resize -
CVE-2026-98380
net/sched: reject IDR error pointers when deleting actions
Same vendor: Linux
-
CVE-2026-98384
bpf: Fix out-of-bounds read of sk_protocol in bpf_sock_destr -
CVE-2026-98383
bpf: Disallow bpf_skb_pull_data() for LWT_SEG6LOCAL -
CVE-2026-98382
bpf: Reject dev-bound-only programs on other devices -
CVE-2026-98381
veth: manage XDP program pointers during channel resize -
CVE-2026-98380
net/sched: reject IDR error pointers when deleting actions
V. Comments for CVE-2026-98299
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