CVE-2026-65624Network attack vector

Memory exhaustion via duplicate HTTP header names

Published Jul 28, 2026 · Updated Jul 28, 2026

Resource exhaustion in Cowboy 2.0.0-pre.4 through 2.17.0 allows remote attackers to exhaust process memory via HTTP/1.1. The cowboy_http parser counts distinct header names rather than header lines, while repeated values are concatenated into an unbounded binary under one map key. No authentication is required; request_timeout bounds each connection, but the default unset max_heap_size permits sustained requests to exhaust Erlang VM memory.

CVSS severity6.9
Medium
EPSS probability0.38%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in Cowboy 2.0.0-pre.4 through 2.17.0 allows remote attackers to exhaust process memory via HTTP/1.1. The cowboy_http parser counts distinct header names rather than header lines, while repeated values are concatenated into an unbounded binary under one map key. No authentication is required; request_timeout bounds each connection, but the default unset max_heap_size permits sustained requests to exhaust Erlang VM memory.

The record

CVE
CVE-2026-65624
Published
Jul 28, 2026
Updated
Jul 28, 2026
Vendor
Nine Nines
Product
Cowboy
Classifications
CWE-770, CAPEC-130, T1499.003
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 28, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 28, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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

  1. Affected versionversion=2.0.0-pre.4 <2.18.0
  2. Affected versionversion=309780a9fda145c262a47ac7811ffd50a0271c5b <3a34d8c1cfd94326466aa16a9017236691dc9c55

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Nine Nines · Cowboyversion=2.0.0-pre.4 <2.18.0; version=309780a9fda145c262a47ac7811ffd50a0271c5b <3a34d8c1cfd94326466aa16a9017236691dc9c55

Published CVSS scores

6.9Erlang Ecosystem FoundationCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-770Allocation of Resources Without Limits or Throttling
CAPEC-130Excessive Allocation
T1499.003Application Exhaustion Flood

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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