CVE-2023-45539Network attack vector

Sensitive-content exposure via fragment-based backend misrouting

Published Nov 28, 2023 · Updated Oct 15, 2024

Improper URI parsing in HAProxy before 2.8.2 allows remote attackers to misroute crafted requests to an unintended backend. The HTTP/1 request-URI parser and path sample fetch treat an unescaped # fragment delimiter as path data, so path_end suffix rules can select the wrong backend. Exposure requires suffix-based routing to a backend that silently trims the fragment; backends that reject the malformed request prevent disclosure.

CVSS severity8.2
High
EPSS probability1.53%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper URI parsing in HAProxy before 2.8.2 allows remote attackers to misroute crafted requests to an unintended backend. The HTTP/1 request-URI parser and path sample fetch treat an unescaped # fragment delimiter as path data, so path_end suffix rules can select the wrong backend. Exposure requires suffix-based routing to a backend that silently trims the fragment; backends that reject the malformed request prevent disclosure.

The record

CVE
CVE-2023-45539
Published
Nov 28, 2023
Updated
Oct 15, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-116, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 28, 2023CVE publishedPublication date reported by the CVE source.
  2. Oct 15, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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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

8.2CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A: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.

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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-116Improper Encoding or Escaping of Output
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

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Your stack

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