CVE-2026-25642
📋 TL;DR
This vulnerability in HedgeDoc allows attackers to host malicious interactive web content, such as fake login forms, via SVG files uploaded to the /uploads/ endpoint due to an overly permissive Content-Security-Policy. It affects HedgeDoc instances prior to version 1.10.6, potentially enabling phishing attacks or other client-side exploits against users accessing uploaded files. Users of vulnerable HedgeDoc deployments are at risk if they interact with maliciously crafted SVG files.
💻 Affected Systems
- HedgeDoc
📦 What is this software?
Hedgedoc by Hedgedoc
⚠️ Risk & Real-World Impact
Worst Case
Attackers could host malicious web content like fake login forms via SVG files, leading to credential theft, session hijacking, or other client-side attacks against users who access the uploaded files.
Likely Case
Phishing attacks where users are tricked into entering credentials into fake forms embedded in SVG files, potentially compromising user accounts or sensitive information.
If Mitigated
If proper controls like strict Content-Security-Policy headers are enforced, the risk is reduced to minimal, preventing execution of malicious scripts or interactive content.
🎯 Exploit Status
Exploitation requires an attacker to upload a malicious SVG file to the /uploads/ endpoint, which is typically accessible if uploads are enabled, making it straightforward but dependent on user interaction.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.10.6
Vendor Advisory: https://github.com/hedgedoc/hedgedoc/security/advisories/GHSA-x74j-jmf9-534w
Restart Required: Yes
Instructions:
1. Backup your HedgeDoc instance and data. 2. Update HedgeDoc to version 1.10.6 or later by following the upgrade instructions at https://github.com/hedgedoc/hedgedoc/releases/tag/1.10.6. 3. Restart the HedgeDoc service to apply the patch.
🔧 Temporary Workarounds
Restrict uploads or disable /uploads endpoint
allTemporarily disable file uploads or block access to the /uploads/ endpoint to prevent malicious SVG files from being hosted.
# Example for nginx: add 'location /uploads/ { deny all; }' to config
# Example for Apache: use 'Redirect 403 /uploads/' in .htaccess
Manually enforce strict Content-Security-Policy headers
allConfigure your web server to apply strict Content-Security-Policy headers for the /uploads/ endpoint to block inline scripts and other risky content.
# Example header: Content-Security-Policy: default-src 'none'; img-src 'self'; style-src 'self'
🧯 If You Can't Patch
- Implement strict Content-Security-Policy headers via web server configuration for the /uploads/ endpoint to mitigate the risk of malicious content execution.
- Monitor and audit uploaded files in the /uploads/ directory for suspicious SVG files and remove any potentially malicious content promptly.
🔍 How to Verify
Check if Vulnerable:
Check the HedgeDoc version; if it is earlier than 1.10.6, it is vulnerable. Also, inspect the Content-Security-Policy headers for the /uploads/ endpoint to see if they are overly permissive.Check Version:
hedgedoc --version or check the version in the HedgeDoc web interface or configuration files.Verify Fix Applied:
After updating to version 1.10.6 or later, verify that the Content-Security-Policy headers for the /uploads/ endpoint are strict and block inline scripts and other risky content.📡 Detection & Monitoring
Log Indicators:
- Unusual uploads of SVG files to the /uploads/ endpoint, especially with large sizes or suspicious names.
- Access logs showing requests to SVG files in /uploads/ followed by user interaction patterns.
Network Indicators:
- HTTP requests to SVG files in the /uploads/ endpoint with parameters or payloads indicative of malicious content.
- Traffic spikes to uploaded SVG files suggesting phishing campaigns.
SIEM Query:
source="hedgedoc_logs" AND (url_path="/uploads/*.svg" OR user_agent CONTAINS "malicious")🔗 References
- https://github.com/hedgedoc/hedgedoc/commit/74daa0e7a1cbfafd9aeb255eaf064dfe47cd401c
- https://github.com/hedgedoc/hedgedoc/commit/b930fe04cee92cd4723044030bb59c36781c7137
- https://github.com/hedgedoc/hedgedoc/releases/tag/1.10.6
- https://github.com/hedgedoc/hedgedoc/security/advisories/GHSA-x74j-jmf9-534w
