CVE-2020-26547
📋 TL;DR
This vulnerability in Monal XMPP client allows remote attackers to inject fake messages into a user's chat history by exploiting insufficient sender verification in MAM (Message Archive Management) and Message Carbon features. Attackers can spoof sender/receiver identities, potentially leading to social engineering attacks. All Monal users running versions before 4.9 are affected.
💻 Affected Systems
- Monal XMPP client
📦 What is this software?
Monal by Monal
⚠️ Risk & Real-World Impact
Worst Case
Attackers can manipulate chat history to impersonate trusted contacts, enabling sophisticated social engineering, credential theft, or spreading misinformation through seemingly legitimate conversations.
Likely Case
Attackers inject malicious messages to trick users into clicking links, downloading malware, or revealing sensitive information by impersonating known contacts.
If Mitigated
With proper network segmentation and monitoring, impact is limited to message spoofing within the XMPP client, though social engineering risks remain.
🎯 Exploit Status
Exploitation requires ability to send XMPP stanzas to victim, which typically requires some level of access to the XMPP network.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 4.9 and later
Vendor Advisory: https://monal.im/blog/cve-2020-26547/
Restart Required: Yes
Instructions:
1. Update Monal to version 4.9 or later from the App Store (iOS) or official website (macOS). 2. Restart the application after update.
🔧 Temporary Workarounds
Disable MAM and Message Carbon
allDisable Message Archive Management and Message Carbon features in XMPP server configuration
Server-specific configuration changes required
🧯 If You Can't Patch
- Disconnect from untrusted XMPP servers or networks
- Use alternative XMPP client with proper sender verification
🔍 How to Verify
Check if Vulnerable:
Check Monal version in app settings. If version is below 4.9, system is vulnerable.Check Version:
Not applicable - check version in Monal app settingsVerify Fix Applied:
Verify Monal version is 4.9 or higher in app settings.📡 Detection & Monitoring
Log Indicators:
- Unusual message patterns in XMPP server logs
- Messages with mismatched sender/receiver metadata
Network Indicators:
- Suspicious XMPP stanza patterns targeting MAM/carbon features
- Unexpected message injection attempts
SIEM Query:
Not applicable - client-side vulnerability