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How the CVE works:
CVE-2025-20378 is an unvalidated redirect vulnerability in Splunk Enterprise and Cloud Platform’s web login endpoint. The `return_to` parameter in the login URL is not properly validated. An unauthenticated attacker can craft a malicious URL with a `return_to` value pointing to an external malicious site. When an authenticated Splunk user visits this crafted URL, the application redirects the user to the attacker-controlled site without validation. This occurs due to insufficient server-side checks on the parameter. The attack requires social engineering to trick the victim into clicking the link. The vulnerability affects Splunk Enterprise versions below 10.0.1, 9.4.5, 9.3.7, 9.2.9, and Splunk Cloud Platform versions below 10.0.2503.5, 9.3.2411.111, and 9.3.2408.121. The redirect can facilitate phishing campaigns, leading to credential theft or malware delivery. Exploitation is limited to authenticated users initiating the request. The flaw is a classic open redirect issue, common in web applications. Patches have been released to validate and restrict redirect destinations.
Platform: Splunk Enterprise Cloud
Version: Below specified versions
Vulnerability: Unvalidated redirect
Severity: Medium
Date: 11/12/2025
Prediction: Patches available now
What Undercode Say:
Analytics:
curl -I “https://target/login?return_to=https://evil.com”
grep -r “return_to” /opt/splunk/etc/
python3 -c “import urllib.parse; print(urllib.parse.quote(‘https://attacker.net’))”
How Exploit:
Craft malicious URL.
Phish authenticated users.
Redirect to evil site.
Protection from this CVE:
Update to fixed versions.
Validate redirect URLs.
Implement allowlisting.
Impact:
Phishing attacks.
Credential theft.
Reputation damage.
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Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
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