CVE-2023-25725Network attack vector

Access-control bypass via empty header names

Published Feb 14, 2023 · Updated Mar 20, 2025

HTTP request smuggling in HAProxy before 2.7.3 allows remote attackers to bypass access controls with malformed HTTP/1 headers. The HTTP/1 parser accepts an empty header field name and truncates the parsed header list, hiding headers already used to determine message framing. Exploitation requires an HTTP/1.0 or HTTP/1.1 proxy chain, where hidden Content-Length or Transfer-Encoding headers can desynchronize downstream request handling.

CVSS severity9.1
Critical
EPSS probability5.45%
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 before 2.7.3 allows remote attackers to bypass access controls with malformed HTTP/1 headers. The HTTP/1 parser accepts an empty header field name and truncates the parsed header list, hiding headers already used to determine message framing. Exploitation requires an HTTP/1.0 or HTTP/1.1 proxy chain, where hidden Content-Length or Transfer-Encoding headers can desynchronize downstream request handling.

The record

CVE
CVE-2023-25725
Published
Feb 14, 2023
Updated
Mar 20, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-444, CAPEC-33, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 14, 2023CVE publishedPublication date reported by the CVE source.
  2. Mar 20, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

9.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
9.1CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/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-444Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
CAPEC-33HTTP Request 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