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Open Redirect CVE-2026-39940

| EUVDEUVD-2026-22011 MEDIUM
URL Redirection to Untrusted Site (Open Redirect) (CWE-601)
2026-04-13 GitHub_M
5.3
CVSS 4.0 · GitHub Advisory
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Severity by source

GitHub Advisory PRIMARY
5.3 MEDIUM
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Primary rating from GitHub Advisory · only source for this CVE.

CVSS VectorGitHub Advisory

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
X

Lifecycle Timeline

6
Patch released
Apr 17, 2026 - 15:33 nvd
Patch available
Patch available
Apr 16, 2026 - 05:29 EUVD
7.0.0
Analysis Generated
Apr 15, 2026 - 12:47 vuln.today
EUVD ID Assigned
Apr 13, 2026 - 16:45 euvd
EUVD-2026-22011
Analysis Generated
Apr 13, 2026 - 16:45 vuln.today
CVE Published
Apr 13, 2026 - 16:34 nvd
MEDIUM 5.3

DescriptionGitHub Advisory

ChurchCRM is an open-source church management system. Prior to 7.0.0, it was possible in many places across the ChurchCRM application to create a link that, when visited by an authenticated user, would redirect them to any URL chosen by an attacker if they clicked 'Cancel' button on the page. For this write-up the DonatedItemEditor.php will be used as an example, however wherever all instances of 'linkBack' should be assessed. This vulnerability is fixed in 7.0.0.

AnalysisAI

Open redirect vulnerability in ChurchCRM prior to 7.0.0 allows authenticated users to be redirected to arbitrary URLs via malicious 'linkBack' parameters across multiple application pages, including DonatedItemEditor.php. An attacker can craft a link embedding an attacker-controlled URL that executes when a victim clicks the 'Cancel' button, enabling phishing and credential harvesting attacks. EPSS scoring (0.04%, percentile 11%) indicates low real-world exploitation probability despite authenticated access requirement.

Technical ContextAI

ChurchCRM is a PHP-based open-source church management system (CPE: cpe:2.3:a:churchcrm:crm). The vulnerability stems from improper validation of the 'linkBack' parameter across multiple editor pages, a classic open redirect scenario classified as CWE-601 (URL Redirection to Untrusted Site). The application fails to restrict or validate the target URL before redirecting authenticated users, allowing an attacker to specify arbitrary external URLs. The vulnerability affects all instances of 'linkBack' usage, with DonatedItemEditor.php cited as a representative example. The attack leverages the application's redirect mechanism to bypass user trust signals (users see a legitimate ChurchCRM domain initially), making it effective for phishing attacks.

RemediationAI

Vendor-released patch: ChurchCRM 7.0.0 and later. Organizations should upgrade ChurchCRM immediately to version 7.0.0 or newer, which includes fixes for all instances of the 'linkBack' parameter vulnerability. Interim mitigation for users unable to upgrade immediately includes restricting email forwarding of internal ChurchCRM links to trusted domains only and implementing email filtering rules to flag external redirects. Detailed patch information and upgrade instructions are available in the GitHub security advisories at https://github.com/ChurchCRM/CRM/security/advisories/GHSA-5g52-rvjf-6wwf and https://github.com/ChurchCRM/CRM/security/advisories/GHSA-v3hj-33xf-qx47.

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CVE-2026-39940 vulnerability details – vuln.today

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