CVE-2026-69203Network attack vector

Service interruption via unlimited HTTP/2 stream allocation

Published Sep 15, 2026 · Updated Sep 15, 2026

Resource exhaustion in http4s Ember before 0.23.35 and 1.0.0-M47 allows remote attackers to interrupt HTTP/2 clients and servers. Ember's HTTP/2 stream handler ignores SETTINGS_MAX_CONCURRENT_STREAMS and retains per-stream state for every peer-created stream until heap exhaustion. Exposure requires .withHttp2 on servers or an Ember client contacting a malicious or compromised HTTP/2 server; enablePush does not block PUSH_PROMISE abuse.

CVSS severity7.5
High
EPSS probability0.46%
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 http4s Ember before 0.23.35 and 1.0.0-M47 allows remote attackers to interrupt HTTP/2 clients and servers. Ember's HTTP/2 stream handler ignores SETTINGS_MAX_CONCURRENT_STREAMS and retains per-stream state for every peer-created stream until heap exhaustion. Exposure requires .withHttp2 on servers or an Ember client contacting a malicious or compromised HTTP/2 server; enablePush does not block PUSH_PROMISE abuse.

The record

CVE
CVE-2026-69203
Published
Sep 15, 2026
Updated
Sep 15, 2026
Vendor
http4s
Product
http4s
Classifications
CWE-770, CWE-400, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 15, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 15, 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=< 0.23.35
  2. Affected versionversion=>= 1.0.0-M1, < 1.0.0-M47

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

http4s · http4sversion=< 0.23.35; version=>= 1.0.0-M1, < 1.0.0-M47

Published CVSS scores

7.5GitHubCVSS: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 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
CWE-400Uncontrolled Resource Consumption
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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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