CVE-2025-48865Public exploitNetwork attack vector

Access control bypass via hop-by-hop header manipulation

Published May 30, 2025 · Updated May 30, 2025

Improper header handling in Fabiolb Fabio before 1.6.6 allows remote attackers to alter trusted forwarding metadata via HTTP requests. The proxy addHeaders function retains client-supplied Connection tokens after adding protected forwarding headers, so hop-by-hop cleanup removes or permits manipulation of those headers before the backend receives the request. Exploitation requires an HTTP route to a backend that trusts the affected metadata; the resulting confusion can bypass backend access controls or alter security decisions.

CVSS severity9.1
Critical
EPSS probability0.49%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper header handling in Fabiolb Fabio before 1.6.6 allows remote attackers to alter trusted forwarding metadata via HTTP requests. The proxy addHeaders function retains client-supplied Connection tokens after adding protected forwarding headers, so hop-by-hop cleanup removes or permits manipulation of those headers before the backend receives the request. Exploitation requires an HTTP route to a backend that trusts the affected metadata; the resulting confusion can bypass backend access controls or alter security decisions.

The record

CVE
CVE-2025-48865
Published
May 30, 2025
Updated
May 30, 2025
Vendor
Fabiolb
Product
Fabio
Classifications
CWE-348, CWE-345, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 30, 2025CVE publishedPublication date reported by the CVE source.
  2. May 30, 2025Record 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=< 1.6.6

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Fabiolb · Fabioversion=< 1.6.6

Published CVSS scores

9.1GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-348Use of Less Trusted Source
CWE-345Insufficient Verification of Data Authenticity
T1190Exploit Public-Facing Application

Public exploit references

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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