Overview
This report provides an analysis of a significant vulnerability in Copyparty, a widely-utilized portable file server. Identified as CVE-2025-54796, this vulnerability could allow an attacker to deadlock the server, potentially compromising the system or leading to data leakage. It is critical for organizations using affected versions of Copyparty to understand the implications of this vulnerability and take immediate actions to mitigate potential risks.
Vulnerability Summary
CVE ID: CVE-2025-54796
Severity: High (7.5 CVSS)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: System deadlock leading to potential system compromise or data leakage
Affected Products
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Product | Affected Versions
Copyparty | Up to but not including 1.18.9
How the Exploit Works
The vulnerability resides in the filter parameter for the “Recent Uploads” page in versions of Copyparty prior to 1.18.9. This parameter allows arbitrary RegExes. If this feature is enabled (which is the default setting), an attacker can craft a filter introducing a complex enough regular expression that would cause the server to enter into an infinite loop or consume excessive resources, thus deadlocking the server.
Conceptual Example Code
The following pseudocode exemplifies how an attacker might exploit this vulnerability:
GET /recent-uploads?filter=(a+)+b HTTP/1.1
Host: target.example.comIn this example, the filter `(a+)+b` is a classic example of a regular expression that can lead to catastrophic backtracking, causing the server to consume excessive resources and enter a deadlock state.
Mitigation
For mitigation, it’s recommended to upgrade to Copyparty version 1.18.9 or later where this vulnerability has been fixed. As a temporary countermeasure, a Web Application Firewall (WAF) or Intrusion Detection System (IDS) can be configured to block or filter requests containing complex or potentially malicious regular expressions.
