CVE-2024-9511
📋 TL;DR
The FluentSMTP WordPress plugin is vulnerable to PHP object injection via deserialization of untrusted input, allowing unauthenticated attackers to inject malicious PHP objects. If a POP chain exists through other installed plugins or themes, this could lead to arbitrary file deletion, data theft, or remote code execution. All WordPress sites using FluentSMTP versions up to 2.2.82 are affected.
💻 Affected Systems
- FluentSMTP – WP SMTP Plugin with Amazon SES, SendGrid, MailGun, Postmark, Google and Any SMTP Provider
⚠️ 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
Remote code execution leading to complete site compromise, data exfiltration, and server takeover if a suitable POP chain exists in the environment.
Likely Case
Denial of service through arbitrary file deletion or limited data exposure if no POP chain is present in the vulnerable plugin itself.
If Mitigated
No impact if the vulnerability is patched or if no POP chain exists in the WordPress environment.
🎯 Exploit Status
No known POP chain exists in the vulnerable plugin itself, requiring attackers to find compatible POP chains in other installed components.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Versions after 2.2.82
Vendor Advisory: https://plugins.trac.wordpress.org/changeset/3194555/
Restart Required: No
Instructions:
1. Log into WordPress admin panel. 2. Navigate to Plugins → Installed Plugins. 3. Find FluentSMTP plugin. 4. Click 'Update Now' if available. 5. Alternatively, download latest version from WordPress repository and manually update.
🔧 Temporary Workarounds
Disable FluentSMTP Plugin
allTemporarily disable the vulnerable plugin until patched
wp plugin deactivate fluent-smtp
Restrict Plugin Access
allUse web application firewall to block access to vulnerable endpoints
🧯 If You Can't Patch
- Implement strict network segmentation to isolate WordPress installation
- Deploy web application firewall with rules to detect and block deserialization attempts
🔍 How to Verify
Check if Vulnerable:
Check WordPress admin panel → Plugins → FluentSMTP → Version. If version is 2.2.82 or lower, system is vulnerable.Check Version:
wp plugin get fluent-smtp --field=versionVerify Fix Applied:
Verify FluentSMTP plugin version is higher than 2.2.82 in WordPress admin panel.📡 Detection & Monitoring
Log Indicators:
- Unusual POST requests to FluentSMTP endpoints
- PHP deserialization errors in WordPress debug logs
- Unexpected file deletion or creation events
Network Indicators:
- HTTP requests containing serialized PHP objects to FluentSMTP-related URLs
- Unusual outbound connections from WordPress server after exploitation
SIEM Query:
source="wordpress.log" AND "fluent-smtp" AND ("unserialize" OR "PHP object")🔗 References
- https://plugins.trac.wordpress.org/browser/fluent-smtp/trunk/app/Models/Logger.php#L157
- https://plugins.trac.wordpress.org/changeset/3194359/
- https://plugins.trac.wordpress.org/changeset/3194555/
- https://www.wordfence.com/threat-intel/vulnerabilities/id/a3deedc4-b939-4c54-8376-95d3728872d4?source=cve
