CVE-2023-25950Network attack vector

Request smuggling via unchecked HTTP/3 header names

Published Apr 11, 2023 · Updated Feb 11, 2025

HTTP request smuggling in HAProxy 2.6.1 through 2.6.7 and 2.7.0 allows remote attackers to alter legitimate requests over HTTP/3. The h3_headers_to_htx function forwards header names without rejecting uppercase letters, spaces, or other non-token characters. Exploitation requires an HTTP/3 frontend and a backend server that interprets the malformed header differently, enabling sensitive-data disclosure or a service interruption.

CVSS severity7.3
High
EPSS probability2.94%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

HTTP request smuggling in HAProxy 2.6.1 through 2.6.7 and 2.7.0 allows remote attackers to alter legitimate requests over HTTP/3. The h3_headers_to_htx function forwards header names without rejecting uppercase letters, spaces, or other non-token characters. Exploitation requires an HTTP/3 frontend and a backend server that interprets the malformed header differently, enabling sensitive-data disclosure or a service interruption.

The record

CVE
CVE-2023-25950
Published
Apr 11, 2023
Updated
Feb 11, 2025
Vendor
HAProxy Technologies
Product
HAProxy
Classifications
CWE-444, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 11, 2023CVE publishedPublication date reported by the CVE source.
  2. Feb 11, 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=version 2.7.0, and version 2.6.1 to 2.6.7

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

HAProxy Technologies · HAProxyversion=version 2.7.0, and version 2.6.1 to 2.6.7

Published CVSS scores

5.6JPCERT/CCCVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L
5.1JPCERT/CCAV:N/AC:H/Au:N/C:P/I:P/A:P
7.3CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
7.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

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-444Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
T1190Exploit Public-Facing Application

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

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo