CVE-2026-43924Network attack vector

Administrator-enabled phishing redirects via unvalidated destinations

Published Jun 3, 2026 · Updated Jun 3, 2026

Open redirect in the FOSSBilling Redirect module before 0.8.0 allows remote authenticated users to send visitors to external sites. The admin API only trims and HTML-escapes destination URLs before Service.php stores them, and Controller/Client.php places the value directly in a 301 Location header without validating its scheme or origin. Administrator access is required to create or modify an entry, and a visitor must follow its legitimate FOSSBilling path, enabling persistently cached phishing redirects.

CVSS severity4.8
Medium
EPSS probability0.26%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Open redirect in the FOSSBilling Redirect module before 0.8.0 allows remote authenticated users to send visitors to external sites. The admin API only trims and HTML-escapes destination URLs before Service.php stores them, and Controller/Client.php places the value directly in a 301 Location header without validating its scheme or origin. Administrator access is required to create or modify an entry, and a visitor must follow its legitimate FOSSBilling path, enabling persistently cached phishing redirects.

The record

CVE
CVE-2026-43924
Published
Jun 3, 2026
Updated
Jun 3, 2026
Vendor
FOSSBilling
Product
FOSSBilling
Classifications
CWE-601, CAPEC-178, T1566.002
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Jun 3, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 3, 2026Record 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=< 0.8.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

FOSSBilling · FOSSBillingversion=< 0.8.0

Published CVSS scores

4.8GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:P/VC:N/VI:N/VA:N/SC:N/SI:L/SA: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.

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
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-601URL Redirection to Untrusted Site ('Open Redirect')
CAPEC-178Cross-Site Flashing
T1566.002Spearphishing Link

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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