CVE-2026-3455
📋 TL;DR
CVE-2026-3455 is a cross-site scripting vulnerability in mailparser versions before 3.9.3 where the textToHtml() function fails to properly sanitize URLs in email content. Attackers can inject malicious JavaScript by adding extra quotes to URLs, potentially executing arbitrary scripts in victims' browsers. This affects any application using vulnerable versions of the mailparser package to process email content.
💻 Affected Systems
- mailparser
📦 What is this software?
Mailparser by Nodemailer
⚠️ Risk & Real-World Impact
Worst Case
Attackers could steal session cookies, perform actions as authenticated users, redirect to malicious sites, or install malware through drive-by downloads.
Likely Case
Attackers could steal user credentials, session tokens, or perform limited actions within the context of the vulnerable email parsing application.
If Mitigated
With proper input validation and output encoding, the impact is limited to potential data leakage from the email parsing context only.
🎯 Exploit Status
The vulnerability is straightforward to exploit with publicly available details. Attackers need to craft malicious email content that gets processed by vulnerable systems.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 3.9.3
Vendor Advisory: https://github.com/nodemailer/mailparser/commit/921a67df4cfb38f0b411037d7b26fbd4d5411b08
Restart Required: No
Instructions:
1. Update mailparser package to version 3.9.3 or later using npm update mailparser. 2. Verify the update with npm list mailparser. 3. Test email parsing functionality to ensure compatibility.
🔧 Temporary Workarounds
Input Sanitization Wrapper
allImplement custom URL sanitization before passing content to textToHtml() function
// JavaScript example: const sanitizedContent = content.replace(/\"(javascript:|data:)/gi, '')
🧯 If You Can't Patch
- Disable or avoid using textToHtml() function on untrusted email content
- Implement Content Security Policy headers to restrict script execution
🔍 How to Verify
Check if Vulnerable:
Check package.json or run npm list mailparser to see if version is below 3.9.3Check Version:
npm list mailparser | grep mailparserVerify Fix Applied:
Verify mailparser version is 3.9.3 or higher with npm list mailparser and test with known malicious email content📡 Detection & Monitoring
Log Indicators:
- Unusual email parsing errors
- Multiple failed parsing attempts
- Log entries showing malformed URLs in email processing
Network Indicators:
- Unusual outbound connections from email processing servers
- Traffic patterns suggesting data exfiltration
SIEM Query:
source="application_logs" AND ("textToHtml" OR "mailparser") AND ("error" OR "malformed" OR "javascript:")