CVE-2025-25186
📋 TL;DR
This vulnerability in Ruby's Net::IMAP library allows a malicious IMAP server to cause denial of service through memory exhaustion. When a client connects to a malicious server, the server can send highly compressed uid-set data that causes the client's response parser to create excessively large arrays, consuming all available memory. This affects Ruby applications using net-imap versions 0.3.2 through 0.3.7, 0.4.0 through 0.4.18, and 0.5.0 through 0.5.5.
💻 Affected Systems
- Ruby net-imap library
⚠️ 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 system memory exhaustion leading to application crash, service disruption, and potential system instability affecting other processes.
Likely Case
IMAP client application crashes or becomes unresponsive when connecting to a malicious server, disrupting email functionality.
If Mitigated
Minimal impact with proper patching or network controls preventing connections to untrusted IMAP servers.
🎯 Exploit Status
Exploitation requires a malicious IMAP server that the client connects to, not client-side code execution.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 0.3.8, 0.4.19, 0.5.6 or higher
Vendor Advisory: https://github.com/ruby/net-imap/security/advisories/GHSA-7fc5-f82f-cx69
Restart Required: Yes
Instructions:
1. Update net-imap gem: `gem update net-imap` 2. Update Gemfile to specify patched version 3. Restart all Ruby applications using net-imap 4. Verify update with `gem list net-imap`
🔧 Temporary Workarounds
Network segmentation
allRestrict IMAP client connections to trusted servers only
Gem version pinning
allPin net-imap to safe versions in Gemfile
gem 'net-imap', '>= 0.3.8', '< 0.4.0'
gem 'net-imap', '>= 0.4.19', '< 0.5.0'
gem 'net-imap', '>= 0.5.6'
🧯 If You Can't Patch
- Implement network controls to only allow IMAP connections to trusted, verified servers
- Monitor application memory usage and restart services if abnormal memory consumption is detected
🔍 How to Verify
Check if Vulnerable:
Check net-imap version with: `gem list net-imap` or `bundle show net-imap`Check Version:
gem list net-imapVerify Fix Applied:
Confirm version is 0.3.8+, 0.4.19+, or 0.5.6+ with: `gem list net-imap | grep -E '0\.(3\.([8-9]|\d{2,})|4\.(19|[2-9]\d)|5\.([6-9]|\d{2,}))'`📡 Detection & Monitoring
Log Indicators:
- Sudden application crashes
- Out of memory errors in Ruby logs
- IMAP connection failures
Network Indicators:
- Connections to unknown or suspicious IMAP servers
- Unusually large IMAP responses
SIEM Query:
source="ruby_app.log" AND ("out of memory" OR "MemoryError" OR "IMAP connection failed")🔗 References
- https://github.com/ruby/net-imap/commit/70e3ddd071a94e450b3238570af482c296380b35
- https://github.com/ruby/net-imap/commit/c8c5a643739d2669f0c9a6bb9770d0c045fd74a3
- https://github.com/ruby/net-imap/commit/cb92191b1ddce2d978d01b56a0883b6ecf0b1022
- https://github.com/ruby/net-imap/security/advisories/GHSA-7fc5-f82f-cx69
