CVE-2026-87734Public exploitNetwork attack vector

Remote denial of service via reassembly queue

Published Sep 9, 2026 · Updated Sep 9, 2026

Denial of service in OCaml utcp before 0.0.6 allows remote attackers to exhaust receiver CPU via out-of-order TCP segments. The reassembly path retains one queue entry per tiny segment and re-folds the entire flat list whenever another segment arrives. A remote peer must complete a normal TCP handshake; keeping the rcv_nxt gap open consumes disproportionate CPU and interrupts service.

CVSS severity7.5
High
EPSS probability0.29%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in OCaml utcp before 0.0.6 allows remote attackers to exhaust receiver CPU via out-of-order TCP segments. The reassembly path retains one queue entry per tiny segment and re-folds the entire flat list whenever another segment arrives. A remote peer must complete a normal TCP handshake; keeping the rcv_nxt gap open consumes disproportionate CPU and interrupts service.

The record

CVE
CVE-2026-87734
Published
Sep 9, 2026
Updated
Sep 9, 2026
Vendor
OCaml
Product
utcp
Classifications
CWE-400, CWE-923, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 9, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <0.0.6

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

OCaml · utcpversion=0 <0.0.6

Published CVSS scores

7.5OCaml security-advisoriesCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
7.5MITRE CNACVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
CWE-923Improper Restriction of Communication Channel to Intended Endpoints
T1499Endpoint Denial of Service

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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