How To Urgent Security Alert: Apache Traffic Server Vulnerability (CVE-2025-49763)
Overview
A critical vulnerability, CVE-2025-49763, has been identified in Apache Traffic Server (ATS) versions 9.0.0–9.2.10 and 10.0.0–10.0.5, affecting the Edge Side Includes (ESI) plugin. This security flaw enables attackers to remotely execute a Denial-of-Service (DoS) attack by exhausting server memory, potentially causing significant downtime and disruption.
Why is this Important?
- Unauthenticated Exploit: Attackers can exploit the vulnerability remotely without needing any authentication.
- High Impact: Commonly used for caching and reverse proxying, Apache Traffic Server’s downtime can significantly impact websites and applications.
- High Severity (CVSS 7.5): Requires immediate action.
Technical Details
Attackers exploit the vulnerability by sending specially crafted requests using the ESI plugin. These requests create endless loops of nested includes, consuming excessive memory resources until the server crashes or stops responding.
Who is Affected?
Organizations using Apache Traffic Server in the following configurations:
- ATS versions 9.0.0–9.2.10 and 10.0.0–10.0.5
- Utilizing the ESI plugin with remote access enabled
- Relying on ATS for caching, reverse-proxying, or load balancing
Recommended Immediate Actions
- Apply Updates: Immediately update your Apache Traffic Server installations to a patched version.
- Disable ESI Plugin Temporarily: If the ESI plugin isn’t crucial, disable it until patches are applied.
- Monitor Server Metrics: Set up monitoring alerts for abnormal memory usage, high CPU loads, and unusual traffic patterns.
- Deploy Additional Security Measures: Implement Web Application Firewalls (WAFs) and rate limiting to defend against exploit attempts.
Additional Considerations
Security teams have also reported another vulnerability (CVE-2025-31698) affecting ATS’s Proxy Protocol, which allows IP-based ACL bypass. Ensure both vulnerabilities are addressed to maintain comprehensive security.
Summary
| Vulnerability | Impact | Action |
|---|---|---|
| CVE-2025-49763 (ESI) | Remote DoS (CVSS 7.5) | Patch ATS immediately |
| CVE-2025-31698 (Proxy) | ACL bypass vulnerability | Apply relevant security patch |
Final Thoughts
Immediate patching and proactive security measures are essential. Don’t wait until it’s too late—secure your Apache Traffic Server installations today.
Keywords: Apache Traffic Server vulnerability, CVE-2025-49763, Apache ATS security patch, DoS attack, cybersecurity alert
