CVE-2025-61962
📋 TL;DR
A vulnerability in fetchmail's SMTP client can cause a crash when processing malformed authentication responses with a 334 status code. This affects systems running fetchmail versions before 6.5.6 that use SMTP authentication. The impact is limited to denial of service through application crashes.
💻 Affected Systems
- fetchmail
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
Fetchmail crashes repeatedly, disrupting email retrieval services and potentially causing mail queue buildup or service unavailability.
Likely Case
Intermittent fetchmail crashes when connecting to SMTP servers that send malformed authentication responses, requiring manual restart of fetchmail processes.
If Mitigated
With proper monitoring and automatic restart mechanisms, impact is limited to brief service interruptions.
🎯 Exploit Status
Exploitation requires ability to send malformed SMTP authentication responses to fetchmail, typically requiring control of the SMTP server or man-in-the-middle position.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 6.5.6
Vendor Advisory: https://www.fetchmail.info/fetchmail-SA-2025-01.txt
Restart Required: Yes
Instructions:
1. Download fetchmail 6.5.6 from official sources. 2. Compile and install following standard procedures. 3. Restart fetchmail daemon or services. 4. Verify version with 'fetchmail --version'.
🔧 Temporary Workarounds
Disable SMTP authentication
linuxConfigure fetchmail to use POP3/IMAP without SMTP authentication if possible
Edit fetchmailrc to remove SMTP authentication options
Use alternative mail retrieval
allTemporarily use different mail retrieval software while patching
🧯 If You Can't Patch
- Implement monitoring and automatic restart for fetchmail processes
- Restrict network access to trusted SMTP servers only
🔍 How to Verify
Check if Vulnerable:
Run 'fetchmail --version' and check if version is below 6.5.6Check Version:
fetchmail --version | head -1Verify Fix Applied:
Run 'fetchmail --version' and confirm version is 6.5.6 or higher📡 Detection & Monitoring
Log Indicators:
- fetchmail crash logs
- segmentation fault messages in system logs
- unexpected fetchmail process termination
Network Indicators:
- Failed SMTP authentication attempts followed by connection termination
SIEM Query:
process.name="fetchmail" AND (event.action="crashed" OR log.level="error")