CVE-2023-22465Network attack vector

Service interruption via malformed typed headers

Published Jan 4, 2023 · Updated Mar 10, 2025

Denial of service in affected http4s releases allows remote attackers to interrupt HTTP services via crafted User-Agent or Server headers. The lazily invoked typed-header parsers encounter a fatal error on certain input instead of safely rejecting the malformed value. Only services that explicitly request a typed User-Agent or Server header invoke the affected parser; weakly typed header access does not.

CVSS severity7.5
High
EPSS probability0.84%
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 affected http4s releases allows remote attackers to interrupt HTTP services via crafted User-Agent or Server headers. The lazily invoked typed-header parsers encounter a fatal error on certain input instead of safely rejecting the malformed value. Only services that explicitly request a typed User-Agent or Server header invoke the affected parser; weakly typed header access does not.

The record

CVE
CVE-2023-22465
Published
Jan 4, 2023
Updated
Mar 10, 2025
Vendor
http4s
Product
http4s
Classifications
CWE-20, T1498
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 4, 2023CVE publishedPublication date reported by the CVE source.
  2. Mar 10, 2025Record 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=>= 0.1.0, < 0.21.34
  2. Affected versionversion=>= 0.22.0, < 0.22.15
  3. Affected versionversion=>= 0.23.0, < 0.23.17
  4. Affected versionversion=>= 1.0.0-M1, < 1.0.0-M38

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

http4s · http4sversion=>= 0.1.0, < 0.21.34; version=>= 0.22.0, < 0.22.15; version=>= 0.23.0, < 0.23.17; version=>= 1.0.0-M1, < 1.0.0-M38

Published CVSS scores

5.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
7.5GitHub, Inc.CVSS: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-20Improper Input Validation
T1498Network Denial of Service

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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