CVE-2024-23185
📋 TL;DR
This vulnerability in Dovecot allows attackers to cause resource exhaustion by sending emails with extremely large headers. The message-header-parser builds an unbounded buffer for header values, leading to excessive memory consumption. All Dovecot versions are affected, though typical mail size limits may restrict exploitation.
💻 Affected Systems
- Dovecot
⚠️ 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
Complete DoS of Dovecot service through memory exhaustion, potentially affecting all users on the server
Likely Case
Self-DoS by users appending large emails, causing memory pressure on backend systems
If Mitigated
Minimal impact if header size restrictions are implemented at the MTA level
🎯 Exploit Status
No known public exploits; exploitation requires sending specially crafted emails
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check vendor advisories for specific patched versions
Vendor Advisory: https://documentation.open-xchange.com/dovecot/security/advisories/csaf/2024/oxdc-adv-2024-0003.json
Restart Required: Yes
Instructions:
1. Check Dovecot version with 'dovecot --version'
2. Update Dovecot using your distribution's package manager
3. Restart Dovecot service: 'systemctl restart dovecot'
🔧 Temporary Workarounds
Implement MTA header size restrictions
linuxConfigure mail transfer agents (Postfix, Exim, Sendmail) to limit maximum header size before emails reach Dovecot
# Postfix example: Add to main.cf
header_size_limit = 102400
🧯 If You Can't Patch
- Implement strict header size limits at MTA level
- Monitor Dovecot memory usage and set alerts for abnormal consumption
🔍 How to Verify
Check if Vulnerable:
Check if running any version of Dovecot without the patchCheck Version:
dovecot --versionVerify Fix Applied:
Verify Dovecot version is updated to patched release and test with large header emails📡 Detection & Monitoring
Log Indicators:
- Unusually high memory usage in Dovecot processes
- Failed email deliveries with large headers
- Process crashes or restarts
Network Indicators:
- Incoming emails with abnormally large headers
- SMTP connections sending oversized header data
SIEM Query:
source="dovecot.log" AND ("out of memory" OR "memory limit exceeded" OR process_resident_memory_bytes > threshold)