Overview
This blog post delves into an important cybersecurity issue that could put a number of websites at risk. The vulnerability, tracked as CVE-2025-53371, affects DiscordNotifications, an extension for MediaWiki. This extension facilitates the sending of notifications of various actions on a wiki to a Discord channel. Cybersecurity researchers have discovered a significant flaw, which if exploited, could lead to Denial of Service (DOS), Server Side Request Forgery (SSRF), and potentially even Remote Code Execution (RCE). This issue is highly critical and, therefore, needs to be taken seriously by all MediaWiki users who have implemented this extension.
Vulnerability Summary
CVE ID: CVE-2025-53371
Severity: Critical (9.1 CVSS Score)
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
DiscordNotifications for MediaWiki | All versions before commit 1f20d850cbcce5b15951c7c6127b87b927a5415e
How the Exploit Works
The vulnerability lies in the DiscordNotifications extension’s ability to send requests via curl and file_get_contents to arbitrary URLs set via $wgDiscordIncomingWebhookUrl and $wgDiscordAdditionalIncomingWebhookUrls. An attacker can exploit this by causing the server to read large files, leading to a DOS attack.
Moreover, if there are internal unprotected APIs that can be accessed through HTTP POST requests, SSRF becomes possible. This could potentially lead to Remote Code Execution (RCE), thereby putting the entire system at risk.
Conceptual Example Code
Suppose an attacker knows the endpoint of an internal unprotected API. They could exploit this vulnerability by sending an HTTP POST request like the following:
POST /internal/api/endpoint HTTP/1.1
Host: target.example.com
Content-Type: application/json
{
"wgDiscordIncomingWebhookUrl": "http://malicious.example.com/largefile",
"wgDiscordAdditionalIncomingWebhookUrls": ["http://malicious.example.com/"]
}In this example, the attacker is causing the server to make a request to their malicious server, which responds with a large file, causing a Denial of Service. Additionally, if the endpoint is not properly secured, this could lead to SSRF or even RCE.
To mitigate this vulnerability, users are advised to apply the patch provided by the vendor, which is available from commit 1f20d850cbcce5b15951c7c6127b87b927a5415e. Alternatively, as a temporary solution, usage of a Web Application Firewall (WAF) or an Intrusion Detection System (IDS) is recommended.