Overview
This report details a significant vulnerability in Apache Traffic Server, identified as CVE-2025-49763. This vulnerability affects versions from 10.0.0 through 10.0.5 and from 9.0.0 through 9.2.10. The issue arises from the ESI plugin not having a limit for maximum inclusion depth, potentially leading to excessive memory consumption if malicious instructions are inserted. If exploited, this vulnerability could lead to system compromise or data leakage.
Vulnerability Summary
CVE ID: CVE-2025-49763
Severity: High (CVSS: 7.5)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: Potential system compromise or data leakage
Affected Products
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Product | Affected Versions
Apache Traffic Server | 10.0.0 – 10.0.5
Apache Traffic Server | 9.0.0 – 9.2.10
How the Exploit Works
The vulnerability is exploited when an attacker manipulates the ESI plugin by inserting malicious instructions. The ESI plugin, due to its lack of a maximum inclusion depth limit, continues to process these instructions, causing excessive memory consumption. This can lead to a system crash or, in some cases, the execution of arbitrary code.
Conceptual Example Code
POST /ESIplugin/endpoint HTTP/1.1
Host: target.example.com
Content-Type: application/json
{ "malicious_instructions": "Insert excessive instructions here to cause memory overflow" }
Mitigation
Users are advised to upgrade to version 9.2.11 or 10.0.6 of Apache Traffic Server, which contain a fix for the issue. Alternatively, as a temporary mitigation, users can apply a vendor patch, or use a Web Application Firewall (WAF) or Intrusion Detection System (IDS) to detect and block the exploit attempts. Furthermore, a new setting for the ESI plugin (–max-inclusion-depth) can be used to limit the inclusion depth and prevent excessive memory consumption.

