CVE-2025-20378
📋 TL;DR
This vulnerability allows unauthenticated attackers to craft malicious URLs that exploit an unvalidated redirect in Splunk Web's login endpoint. When authenticated users click these links, they can be redirected to external malicious sites. Affected systems include 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.
💻 Affected Systems
- Splunk Enterprise
- Splunk Cloud Platform
📦 What is this software?
Splunk by Splunk
Splunk by Splunk
Splunk by Splunk
Splunk by Splunk
⚠️ Risk & Real-World Impact
Worst Case
Attackers could redirect authenticated users to phishing sites that steal credentials or deliver malware, potentially leading to full Splunk environment compromise.
Likely Case
Users are redirected to phishing pages that attempt to steal Splunk credentials or session tokens.
If Mitigated
With proper user awareness training and web filtering, the impact is limited to potential credential theft from individual users.
🎯 Exploit Status
Exploitation requires social engineering to trick authenticated users into clicking malicious URLs.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Splunk Enterprise: 10.0.1, 9.4.5, 9.3.7, 9.2.9; Splunk Cloud Platform: 10.0.2503.5, 9.3.2411.111, 9.3.2408.121
Vendor Advisory: https://advisory.splunk.com/advisories/SVD-2025-1101
Restart Required: Yes
Instructions:
1. Download appropriate patch version from Splunk downloads portal. 2. Backup current installation. 3. Apply patch following Splunk upgrade documentation. 4. Restart Splunk services.
🔧 Temporary Workarounds
Input Validation Filter
allImplement web application firewall or reverse proxy rules to filter malicious return_to parameter values.
User Awareness Training
allEducate users about phishing risks and not clicking suspicious links in Splunk-related emails or messages.
🧯 If You Can't Patch
- Implement network segmentation to restrict Splunk web interface access to trusted users only.
- Deploy web filtering solutions to block known malicious domains and detect phishing attempts.
🔍 How to Verify
Check if Vulnerable:
Check Splunk version via web interface or command line; compare against affected versions list.Check Version:
On Splunk server: splunk versionVerify Fix Applied:
Verify installed version matches or exceeds patched versions listed in advisory.📡 Detection & Monitoring
Log Indicators:
- Unusual redirect patterns in web access logs
- Multiple failed login attempts followed by successful redirects
Network Indicators:
- Outbound connections to suspicious domains following Splunk web access
SIEM Query:
index=_internal sourcetype=splunkd_access uri=*/en-US/account/login* return_to=* | stats count by clientip, uri