CVE-2025-46736
📋 TL;DR
This CVE describes a timing attack vulnerability in Umbraco CMS that allows attackers to determine whether specific user accounts exist by analyzing post-login API response times. This affects all Umbraco installations prior to versions 10.8.10 and 13.8.1. The vulnerability enables user enumeration, which can facilitate targeted attacks.
💻 Affected Systems
- Umbraco CMS
📦 What is this software?
Umbraco Cms by Umbraco
Umbraco Cms by Umbraco
⚠️ Risk & Real-World Impact
Worst Case
Attackers can enumerate all valid user accounts, enabling targeted brute-force attacks, credential stuffing, or social engineering against identified users.
Likely Case
Attackers identify valid administrative or user accounts, then conduct focused password attacks against those accounts.
If Mitigated
With strong password policies, account lockouts, and monitoring, impact is limited to user enumeration without successful account compromise.
🎯 Exploit Status
Timing attacks require precise measurement capabilities but tools exist to automate this. No authentication is required to attempt exploitation.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 10.8.10 or 13.8.1
Vendor Advisory: https://github.com/umbraco/Umbraco-CMS/security/advisories/GHSA-4g8m-5mj5-c8xg
Restart Required: Yes
Instructions:
1. Backup your Umbraco installation and database. 2. Update to Umbraco version 10.8.10 (for v10) or 13.8.1 (for v13). 3. Restart the application. 4. Test authentication functionality.
🔧 Temporary Workarounds
No official workarounds
allThe vendor states no known workarounds exist. Patching is the only solution.
🧯 If You Can't Patch
- Implement rate limiting and account lockout policies to mitigate brute-force attacks following enumeration
- Monitor authentication logs for unusual patterns of login attempts against multiple usernames
🔍 How to Verify
Check if Vulnerable:
Check your Umbraco version. If it's below 10.8.10 (for v10) or below 13.8.1 (for v13), you are vulnerable.Check Version:
Check the Umbraco version in the admin dashboard or examine the web.config/umbraco.xml file.Verify Fix Applied:
Verify the Umbraco version is 10.8.10 or higher (for v10) or 13.8.1 or higher (for v13). Test that login attempts return consistent timing regardless of account existence.📡 Detection & Monitoring
Log Indicators:
- Multiple failed login attempts with different usernames from same source
- Unusual timing patterns in authentication logs
Network Indicators:
- Repeated POST requests to login endpoints with varying usernames
- Consistent timing patterns in authentication traffic
SIEM Query:
source="umbraco_logs" AND (event="login_failed" OR event="authentication") | stats count by src_ip, username | where count > threshold