CVE-2025-53371: DiscordNotifications DOS Vulnerability

CVE-2025-53371 Overview

CVE-2025-53371 is a critical Server-Side Request Forgery (SSRF) vulnerability in the DiscordNotifications extension for MediaWiki. This extension sends notifications of wiki actions to Discord channels, but fails to properly validate webhook URLs configured via $wgDiscordIncomingWebhookUrl and $wgDiscordAdditionalIncomingWebhookUrls parameters.

The vulnerability allows attackers to manipulate these configuration parameters to send HTTP requests to arbitrary URLs using curl or file_get_contents. This can lead to Denial of Service (DoS) attacks by forcing the server to read large files, SSRF exploitation against internal unprotected APIs, and potentially Remote Code Execution (RCE) if internal services accept malicious POST requests.

Critical Impact

This SSRF vulnerability enables attackers to access internal network resources, cause DoS through resource exhaustion, and potentially achieve RCE by targeting unprotected internal APIs.

Affected Products

• MediaWiki DiscordNotifications Extension (versions prior to commit 1f20d850cbcce5b15951c7c6127b87b927a5415e)

Discovery Timeline

• 2025-07-10 - CVE-2025-53371 published to NVD
• 2025-07-15 - Last updated in NVD database

Technical Details for CVE-2025-53371

Vulnerability Analysis

This vulnerability stems from insufficient URL validation in the DiscordNotifications extension. The extension is designed to send notifications to Discord webhook endpoints when wiki actions occur. However, the implementation failed to restrict the webhook URLs to legitimate Discord endpoints, allowing arbitrary URL targets.

The vulnerability is classified under CWE-400 (Uncontrolled Resource Consumption), though it encompasses broader SSRF attack capabilities. The network-accessible attack vector with low complexity makes this vulnerability particularly dangerous in environments where the MediaWiki instance can reach internal network resources.

Root Cause

The root cause is the absence of URL validation before initiating HTTP requests to webhook endpoints. The extension blindly trusts the configured webhook URLs without verifying they point to legitimate Discord API endpoints. This allows attackers with configuration access to specify internal URLs, cloud metadata endpoints, or other sensitive resources.

Attack Vector

An attacker with the ability to modify MediaWiki configuration parameters can exploit this vulnerability by:

1. Setting $wgDiscordIncomingWebhookUrl or $wgDiscordAdditionalIncomingWebhookUrls to point to internal network resources
2. Triggering wiki actions that cause notifications to be sent
3. The server then makes HTTP POST requests to the attacker-controlled URL targets

This enables reconnaissance of internal services, data exfiltration via POST requests, and potential RCE if vulnerable internal services are accessible.

The security patch introduces URL validation using MediaWiki's UrlUtils service and adds proper logging capabilities through LoggerFactory:

 use Flow\Model\UUID;
 use MediaWiki\Config\ServiceOptions;
 use MediaWiki\Deferred\DeferredUpdates;
+use MediaWiki\Logger\LoggerFactory;
 use MediaWiki\Permissions\PermissionManager;
 use MediaWiki\Registration\ExtensionRegistry;
 use MediaWiki\Title\Title;
 use MediaWiki\User\UserGroupManager;
 use MediaWiki\User\UserIdentity;
+use MediaWiki\Utils\UrlUtils;
 use MessageLocalizer;
+use Psr\Log\LoggerInterface;
 use WikiPage;

 class DiscordNotifier {

Source: GitHub Commit Update

The service wiring was also updated to inject the UrlUtils service for proper URL validation:

 				$services->getConfigFactory()->makeConfig( 'DiscordNotifications' )
 			),
 			$services->getPermissionManager(),
-			$services->getUserGroupManager()
+			$services->getUserGroupManager(),
+			$services->getUrlUtils()
 		);
 	},
 ];

Source: GitHub Commit Update

Detection Methods for CVE-2025-53371

Indicators of Compromise

• Unexpected outbound HTTP POST requests from the MediaWiki server to internal IP addresses or non-Discord endpoints
• Configuration changes to $wgDiscordIncomingWebhookUrl or $wgDiscordAdditionalIncomingWebhookUrls pointing to internal resources
• Unusual network traffic patterns from the web server to internal services or cloud metadata endpoints (e.g., 169.254.169.254)
• Server performance degradation due to requests to large file endpoints or slow-responding internal services

Detection Strategies

• Monitor outbound HTTP traffic from MediaWiki servers for requests to non-Discord API endpoints
• Implement network segmentation rules that alert on MediaWiki servers attempting to contact internal services directly
• Review MediaWiki configuration files and database for unauthorized webhook URL modifications
• Deploy web application firewall (WAF) rules to detect SSRF patterns in request payloads

Monitoring Recommendations

• Enable detailed logging for the DiscordNotifications extension to track all outbound webhook requests
• Configure network monitoring to alert on connections from MediaWiki to internal RFC 1918 addresses
• Implement file integrity monitoring on MediaWiki configuration files to detect unauthorized changes
• Set up alerts for unusual resource consumption patterns that may indicate DoS exploitation

How to Mitigate CVE-2025-53371

Immediate Actions Required

• Update the DiscordNotifications extension to include commit 1f20d850cbcce5b15951c7c6127b87b927a5415e or later
• Audit current webhook URL configurations to ensure they only point to legitimate Discord webhook endpoints
• Restrict access to MediaWiki configuration settings to trusted administrators only
• Implement network-level egress filtering to limit outbound connections from the MediaWiki server

Patch Information

The vulnerability is fixed in commit 1f20d850cbcce5b15951c7c6127b87b927a5415e. The patch introduces URL validation using MediaWiki's UrlUtils service to ensure webhook URLs are legitimate before sending requests. Administrators should update to the latest version of the DiscordNotifications extension from the official Miraheze repository.

For technical details about the vulnerability and the fix, refer to the GitHub Security Advisory GHSA-gvfx-p3h5-qf65.

Workarounds

• If immediate patching is not possible, disable the DiscordNotifications extension temporarily until the update can be applied
• Implement network-level restrictions to only allow the MediaWiki server to connect to Discord's API endpoints (discord.com, discordapp.com)
• Configure a forward proxy for outbound HTTP requests with strict allowlisting of permitted destination hosts
• Monitor and restrict MediaWiki configuration access to prevent unauthorized webhook URL modifications

# Example iptables rules to restrict outbound connections to Discord only
# Apply to MediaWiki server to limit SSRF impact
iptables -A OUTPUT -p tcp -d discord.com --dport 443 -j ACCEPT
iptables -A OUTPUT -p tcp -d discordapp.com --dport 443 -j ACCEPT
iptables -A OUTPUT -p tcp --dport 443 -m owner --uid-owner www-data -j DROP