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CVE-2026-98299ModerateLocalRevised 21 Oct

tcp: do not let tcp_rmem be set below 4096

MSRC advisory NVD CVE.org

Assessment

Severity
Moderate
CVSS base score
5.5CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H/E:U
Impact
Not stated
EPSS · 30-day forecast
No EPSS score collected
Public detection template
No Nuclei template is listed in the current collected catalog
Exploitation detected
Unknown: not stated by MSRC
Exploitability
Not assessed
Publicly disclosed
Unknown: not stated by MSRC
Customer action
Required: follow the MSRC remediation guidance
Component
Mariner
Weakness
—
Issued by
Linux
Published
7 Oct 2026 · October 2026
Last revised
21 Oct 2026Information published.
CVSS 3.1 base metricsRed raises the risk · green lowers it
Attack vector
LocalAV:L
Attack complexity
LowAC:L
Privileges required
LowPR:L
User interaction
NoneUI:N
Scope
UnchangedS:U
Confidentiality
NoneC:N
Integrity
NoneI:N
Availability
HighA:H

Updates that fix it

0 KBs

No KB listed

No KB update is listed in the collected MSRC record. Check the MSRC advisory for product releases and other remedies.

Affected products

Open Source Software
1 affected product
  • azl3 kernel 6.6.157.1-1 on Azure Linux 3.0

What changed

  1. Detection template: Unknown: detection-template evidence is incomplete or retained → No Nuclei template listed
  2. Detection template: No Nuclei template listed → Unknown: detection-template evidence is incomplete or retained
  3. Detection template: Unknown: detection-template evidence is incomplete or retained → No Nuclei template listed
  4. Detection template: No Nuclei template listed → Unknown: detection-template evidence is incomplete or retained
  5. Detection template: No Nuclei template listed · Customer action: Required: apply the update → Required: follow the MSRC remediation guidance · Public disclosure: No → Unknown: not stated by MSRC · Exploitation detected: Not reported by MSRC → Unknown: not stated by MSRC
  6. Detection template: Unknown: exploit-code evidence is incomplete or retained → No Nuclei template listed · CISA KEV: Unknown: catalog evidence is incomplete or retained → Not listed in the collected catalog
  7. Detection template: No Nuclei template listed → Unknown: exploit-code evidence is incomplete or retained · CISA KEV: Not listed in the collected catalog → Unknown: catalog evidence is incomplete or retained
Page history

Changes are dated when recorded; day views use the last saved version from that UTC day, and citations stay fixed.

Cite this version
Field-level log (38)

Up to 100 recent field edits are shown; older edits may be outside retention.

  1. 6 Nov 2026 · 17:32:22 UTC Public detection templateUnknown: detection-template evidence is incomplete or retained → No Nuclei template listed
  2. 6 Nov 2026 · 17:32:22 UTC Source coverage: public-exploit-codeIncomplete → Current
  3. 6 Nov 2026 · 17:32:22 UTC Source coverage: first-epssIncomplete → Current
  4. 6 Nov 2026 · 17:32:22 UTC Source coverage: msrc-cvrfIncomplete → Current
  5. 6 Nov 2026 · 16:31:02 UTC Public detection templateNo Nuclei template listed → Unknown: detection-template evidence is incomplete or retained
  6. 6 Nov 2026 · 16:31:02 UTC Source coverage: public-exploit-codeCurrent → Incomplete
  7. 6 Nov 2026 · 16:31:02 UTC Source coverage: first-epssCurrent → Incomplete
  8. 6 Nov 2026 · 16:31:02 UTC Source coverage: msrc-cvrfCurrent → Incomplete
  9. 2 Nov 2026 · 17:30:39 UTC Public detection templateUnknown: detection-template evidence is incomplete or retained → No Nuclei template listed
  10. 2 Nov 2026 · 17:30:39 UTC Source coverage: public-exploit-codeIncomplete → Current
  11. 2 Nov 2026 · 17:30:39 UTC Source coverage: first-epssIncomplete → Current
  12. 2 Nov 2026 · 17:30:39 UTC Source coverage: msrc-cvrfIncomplete → Current
  13. 2 Nov 2026 · 16:27:39 UTC Public detection templateNo Nuclei template listed → Unknown: detection-template evidence is incomplete or retained
  14. 2 Nov 2026 · 16:27:39 UTC Source coverage: public-exploit-codeCurrent → Incomplete
  15. 2 Nov 2026 · 16:27:39 UTC Source coverage: first-epssCurrent → Incomplete
  16. 2 Nov 2026 · 16:27:39 UTC Source coverage: msrc-cvrfCurrent → Incomplete
  17. 29 Oct 2026 · 20:19:26 UTC Public detection templateNo Nuclei template listed
  18. 29 Oct 2026 · 20:19:26 UTC EPSSNot scored → No EPSS score collected
  19. 29 Oct 2026 · 20:19:26 UTC Customer actionRequired: apply the update → Required: follow the MSRC remediation guidance
  20. 29 Oct 2026 · 20:19:26 UTC Publicly disclosedNo → Unknown: not stated by MSRC
  21. 29 Oct 2026 · 20:19:26 UTC Exploitation detectedNot reported by MSRC → Unknown: not stated by MSRC
  22. 23 Oct 2026 · 09:33:49 UTC Public exploit codeUnknown: exploit-code evidence is incomplete or retained → No Nuclei template listed
  23. 23 Oct 2026 · 09:33:49 UTC CISA KEVUnknown: catalog evidence is incomplete or retained → Not listed in the collected catalog
  24. 23 Oct 2026 · 09:33:49 UTC Source coverage: public-exploit-codeIncomplete → Current
  25. 23 Oct 2026 · 09:33:49 UTC Source coverage: first-epssIncomplete → Current
  26. 23 Oct 2026 · 09:33:49 UTC Source coverage: cisa-kevIncomplete → Current
  27. 23 Oct 2026 · 09:33:49 UTC Source coverage: msrc-cvrfIncomplete → Current
  28. 23 Oct 2026 · 08:31:50 UTC Public exploit codeNo Nuclei template listed → Unknown: exploit-code evidence is incomplete or retained
  29. 23 Oct 2026 · 08:31:50 UTC CISA KEVNot listed in the collected catalog → Unknown: catalog evidence is incomplete or retained
  30. 23 Oct 2026 · 08:31:50 UTC Source coverage: public-exploit-codeCurrent → Incomplete
  31. 23 Oct 2026 · 08:31:50 UTC Source coverage: first-epssCurrent → Incomplete
  32. 23 Oct 2026 · 08:31:50 UTC Source coverage: cisa-kevCurrent → Incomplete
  33. 23 Oct 2026 · 08:31:50 UTC Source coverage: msrc-cvrfCurrent → Incomplete
  34. 21 Oct 2026 · 20:45:25 UTC Last revised15 Oct 2026 02:09 UTC → 21 Oct 2026 18:38 UTC
  35. 18 Oct 2026 · 14:54:30 UTC Link: October 2026/security?release=2026-Oct#cves
  36. 15 Oct 2026 · 07:14:54 UTC Last revised13 Oct 2026 16:59 UTC → 15 Oct 2026 02:09 UTC
  37. 14 Oct 2026 · 11:22:42 UTC Last revised7 Oct 2026 01:06 UTC → 13 Oct 2026 16:59 UTC
  38. 14 Oct 2026 · 11:22:42 UTC Source coverage: msrc-cvrfIncomplete → Current

Explore global source statements, affected packages and advisory history for CVE-2026-98299. The catalog has a separate collection scope from Microsoft release records.

Collected exploitation and prediction evidence

Risk source coverage

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

cve-program · CVE-2026-98299

Published

tcp: do not let tcp_rmem be set below 4096

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 published
6 Oct 2026 08:45:57 UTC
Source modified
19 Oct 2026 09:17:10 UTC
Observed here
23 Oct 2026 15:48:27 UTC
Source terms
CVE Program Terms of Use

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