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CVE-2025-53645: Denial of Service Vulnerability in Zimbra Collaboration Suite

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Overview

This report details a high-severity vulnerability, CVE-2025-53645, found in the Zimbra Collaboration Suite (ZCS). This vulnerability affects versions of ZCS prior to 9.0.0 Patch 46, 10.0.x before 10.0.15, and 10.1.x before 10.1.9. It poses a significant threat as it allows an unauthenticated remote attacker to cause a denial of service (DoS) condition by sending specially crafted GET requests.

Vulnerability Summary

CVE ID: CVE-2025-53645
Severity: High, CVSS Score 7.5
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: Denial of Service, potential system compromise, or data leakage

Affected Products

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Product | Affected Versions

Zimbra Collaboration Suite | Before 9.0.0 Patch 46
Zimbra Collaboration Suite | 10.0.x before 10.0.15
Zimbra Collaboration Suite | 10.1.x before 10.1.9

How the Exploit Works

The vulnerability arises due to the improper handling of excessive, comma-separated path segments in both the Webmail interface and the Admin Console of the Zimbra Collaboration Suite. An unauthenticated remote attacker can exploit this vulnerability by sending specially crafted GET requests with excessive path segments. This triggers redundant processing and inflated responses, leading to uncontrolled resource consumption and ultimately, denial of service.

Conceptual Example Code

Below is a conceptual example of how an attacker might exploit this vulnerability through a GET request.

GET /zimbra/,/,/,/,/,/,/,/,/,/,/,/,/,/,/ HTTP/1.1
Host: target.example.com

This request floods the Zimbra server with redundant processing tasks, leading to resource exhaustion and ultimately, a denial of service.

Mitigation Guidance

The best course of action to mitigate this vulnerability is to apply the vendor-supplied patch. If applying the patch is not immediately feasible, using a Web Application Firewall (WAF) or Intrusion Detection System (IDS) can serve as a temporary mitigation measure. It is highly recommended to prioritize the patch application to ensure the security of the affected systems.

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Disclaimer:

The information and code presented in this article are provided for educational and defensive cybersecurity purposes only. Any conceptual or pseudocode examples are simplified representations intended to raise awareness and promote secure development and system configuration practices.

Do not use this information to attempt unauthorized access or exploit vulnerabilities on systems that you do not own or have explicit permission to test.

Ameeba and its authors do not endorse or condone malicious behavior and are not responsible for misuse of the content. Always follow ethical hacking guidelines, responsible disclosure practices, and local laws.

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