CVE-2025-8760: Critical Buffer Overflow Vulnerability in INSTAR 2K+ and 4K 3.11.1 Build 1124

Overview

A severe vulnerability, CVE-2025-8760, has been identified in INSTAR’s 2K+ and 4K 3.11.1 Build 1124. This particular vulnerability affects the base64_decode function of the fcgi_server component. By manipulating the ‘Authorization’ argument, an attacker may cause a buffer overflow. This vulnerability is significant due to its potential for remote initiation, allowing attackers to potentially compromise systems or leak data from afar. Given its high severity score, it is crucial for users and administrators to understand the nature of this vulnerability and take appropriate action.

Vulnerability Summary

CVE ID: CVE-2025-8760
Severity: Critical, CVSS score 9.8
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: Potential system compromise or data leakage

Affected Products

Product | Affected Versions

INSTAR 2K+ | 3.11.1 Build 1124
INSTAR 4K | 3.11.1 Build 1124

How the Exploit Works

This vulnerability exploits the base64_decode function in the fcgi_server component of the affected INSTAR products. Specifically, an attacker can overly manipulate the ‘Authorization’ argument, causing a buffer overflow. A buffer overflow occurs when more data is written to a buffer than it can handle, causing it to overflow into adjacent memory spaces. In this case, the buffer overflow can potentially overwrite critical data or execute malicious code, leading to system compromise or data leakage.

Conceptual Example Code

While the specific exploit code is not available, below is a conceptual example of how an HTTP request might be manipulated to exploit this vulnerability:

POST /fcgi_server/base64_decode HTTP/1.1
Host: target.example.com
Authorization: Basic [Overly long base64 encoded string]

In this example, the `[Overly long base64 encoded string]` represents a base64 string that, when decoded, is larger than the buffer in the base64_decode function can handle. When the function attempts to decode this string, it causes a buffer overflow, potentially leading to unauthorized code execution or other unintended behavior.

Mitigation Guidance

Customers using affected versions of INSTAR 2K+ and 4K are advised to apply the vendor patch as soon as it becomes available. In the absence of a patch, or as a temporary measure, a Web Application Firewall (WAF) or an Intrusion Detection System (IDS) could be used to mitigate the vulnerability. These systems can be configured to block or alert on suspicious activity related to this vulnerability, such as unusually large ‘Authorization’ headers in HTTP requests to the fcgi_server component.