CVE-2026-25126
📋 TL;DR
PolarLearn's vote API route accepts arbitrary string values for the 'direction' parameter due to missing runtime validation. Attackers can send unexpected values that bypass intended business logic, causing votes to be recorded incorrectly. This affects all PolarLearn instances running versions before 0-PRERELEASE-15.
💻 Affected Systems
- PolarLearn
📦 What is this software?
Polarlearn by Polarlearn
⚠️ Risk & Real-World Impact
Worst Case
Attackers manipulate voting outcomes by sending invalid direction values, undermining forum integrity and potentially enabling coordinated manipulation of content visibility or rankings.
Likely Case
Limited manipulation of individual vote counts on forum posts, potentially affecting content sorting or user reputation systems.
If Mitigated
Proper input validation restricts direction to only 'up', 'down', or null values, preventing business logic bypass.
🎯 Exploit Status
Exploitation requires API access but is technically simple once authenticated.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 0-PRERELEASE-15
Vendor Advisory: https://github.com/polarnl/PolarLearn/security/advisories/GHSA-ghpx-5w2p-p3qp
Restart Required: Yes
Instructions:
1. Update PolarLearn to version 0-PRERELEASE-15 or later. 2. Restart the application server. 3. Verify the fix by testing the vote API with invalid direction values.
🔧 Temporary Workarounds
Input Validation Middleware
allAdd runtime validation to reject non-'up', non-'down', and non-null direction values before processing.
Implement validation in the vote API route handler to check direction parameter
API Gateway Filtering
allUse an API gateway or WAF to block requests with invalid direction values.
Configure WAF rules to reject POST /api/v1/forum/vote with direction not in ['up','down',null]
🧯 If You Can't Patch
- Restrict API access to trusted users only using authentication and authorization controls.
- Monitor vote API logs for unusual patterns or invalid direction values.
🔍 How to Verify
Check if Vulnerable:
Send a POST request to /api/v1/forum/vote with direction set to an arbitrary string (e.g., 'x'). If the request succeeds and affects vote data, the system is vulnerable.Check Version:
Check the PolarLearn version in the application interface or configuration files.Verify Fix Applied:
After patching, repeat the vulnerable test. The request should be rejected or handled appropriately without persisting invalid values.📡 Detection & Monitoring
Log Indicators:
- API logs showing POST /api/v1/forum/vote requests with direction values other than 'up', 'down', or null.
- Unexpected vote data entries in database logs.
Network Indicators:
- HTTP POST requests to the vote endpoint with unusual direction parameters in the JSON body.
SIEM Query:
source='polarlearn' AND path='/api/v1/forum/vote' AND direction NOT IN ('up','down',null)