Overview
CVE-2025-6704 is a critical vulnerability that exists in the Secure PDF eXchange (SPX) feature of Sophos Firewall. This vulnerability, if exploited, could allow an attacker to execute remote code without authentication, potentially leading to system compromise or data leakage. Users utilizing Sophos Firewall versions below 21.0 MR2 (21.0.2) that run in High Availability (HA) mode combined with a specific SPX configuration are affected. The severity of this vulnerability makes it imperative for security administrators and IT professionals to prioritize its mitigation.
Vulnerability Summary
CVE ID: CVE-2025-6704
Severity: Critical (CVSS: 9.8)
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
Sophos Firewall | Versions older than 21.0 MR2 (21.0.2)
How the Exploit Works
The vulnerability lies in the SPX feature of Sophos Firewall. When the firewall runs in High Availability mode with a specific configuration of SPX enabled, it exposes an arbitrary file writing flaw. This vulnerability can be exploited by a remote attacker over the network without requiring any form of authentication or user interaction. Once exploited, this vulnerability allows the attacker to execute arbitrary code on the system, potentially leading to a system compromise or data leakage.
Conceptual Example Code
Given the nature of the vulnerability, an attacker could exploit it by sending a specifically crafted HTTP request to the vulnerable endpoint. Below is a conceptual example of what this HTTP request might look like:
POST /sophos/spx/vulnerable/endpoint HTTP/1.1
Host: target.example.com
Content-Type: application/json
{ "malicious_payload": "arbitrary_code_to_execute" }In this example, the “malicious_payload” would contain the arbitrary code that the attacker wants to execute on the system. Once the request is processed by the server, the code is written to an arbitrary file and executed, leading to potential system compromise or data leakage.
Finally, it is important to note that this is a high-severity vulnerability which requires immediate attention. The recommended mitigation steps include applying the vendor patch or using Web Application Firewall (WAF) or Intrusion Detection System (IDS) as a temporary measure.