CVE-2026-5762: MediaWiki ReportIncident Extension DoS Flaw

CVE-2026-5762 Overview

CVE-2026-5762 is a resource exhaustion vulnerability in the MediaWiki ReportIncident Extension developed by Wikimedia Foundation. The vulnerability stems from improper allocation of resources without limits or throttling, which can be exploited to conduct HTTP Denial of Service (DoS) attacks against affected MediaWiki installations.

The ReportIncident Extension fails to implement proper rate limiting or resource constraints when handling requests, allowing an authenticated attacker to exhaust server resources through repeated requests. This issue has been remediated only on the master branch, meaning production deployments running older versions remain vulnerable until updated.

Critical Impact

Authenticated attackers can exhaust server resources through unlimited request allocation, causing denial of service conditions that impact wiki availability for legitimate users.

Affected Products

• MediaWiki ReportIncident Extension (versions prior to master branch fix)
• MediaWiki installations using the ReportIncident Extension
• Wikimedia Foundation platforms utilizing the affected extension

Discovery Timeline

• 2026-04-07 - CVE-2026-5762 published to NVD
• 2026-04-08 - Last updated in NVD database

Technical Details for CVE-2026-5762

Vulnerability Analysis

This vulnerability is classified under CWE-770 (Allocation of Resources Without Limits or Throttling). The ReportIncident Extension lacks proper safeguards to prevent excessive resource consumption when processing incident report requests. Without rate limiting mechanisms in place, the extension allows authenticated users to submit an unlimited number of requests, which can overwhelm server resources including memory, CPU cycles, and network bandwidth.

The network-accessible nature of this vulnerability means that any authenticated user with access to the ReportIncident functionality can potentially exploit this weakness remotely. The attack does not require elevated privileges beyond basic user authentication, making it accessible to a wide range of potential attackers.

Root Cause

The root cause of CVE-2026-5762 lies in the absence of resource throttling mechanisms within the ReportIncident Extension's request handling logic. The extension processes incident reports without implementing:

• Request rate limiting per user or session
• Maximum concurrent request constraints
• Resource consumption monitoring and caps
• Queueing mechanisms to manage request volume

This design oversight allows attackers to flood the extension with requests faster than the server can process them, leading to resource exhaustion.

Attack Vector

The attack vector for this vulnerability is network-based, requiring low privilege (authenticated user) access. An attacker can exploit this vulnerability by:

1. Authenticating to a MediaWiki instance with the ReportIncident Extension enabled
2. Initiating a high volume of incident report submissions
3. Overwhelming the server's ability to process requests, causing degraded performance or complete unavailability

The vulnerability affects both the primary system and potentially connected systems, as indicated by the scope considerations in the CVSS assessment. The attack can be automated using simple scripting techniques to maximize the rate of malicious requests.

Technical details and the remediation patch can be reviewed in the Wikimedia Code Change Log and the Wikimedia Task Discussion.

Detection Methods for CVE-2026-5762

Indicators of Compromise

• Abnormally high request volumes to ReportIncident Extension endpoints from single user accounts
• Unusual patterns of incident report submissions occurring in rapid succession
• Server performance degradation coinciding with spikes in ReportIncident activity
• Memory and CPU utilization anomalies on MediaWiki servers

Detection Strategies

• Implement monitoring for request rates to the ReportIncident Extension API endpoints
• Configure web application firewall (WAF) rules to detect and alert on high-frequency POST requests to incident reporting functions
• Enable server-side logging to track user activity patterns and identify potential abuse
• Deploy anomaly detection to identify deviations from baseline ReportIncident usage patterns

Monitoring Recommendations

• Set up real-time alerts for unusual spikes in HTTP requests to MediaWiki incident reporting endpoints
• Monitor server resource utilization (CPU, memory, network) for sustained abnormal consumption
• Track authentication events and correlate with subsequent high-volume activity
• Implement log aggregation to centralize visibility across distributed MediaWiki deployments

How to Mitigate CVE-2026-5762

Immediate Actions Required

• Update the ReportIncident Extension to the latest version from the master branch containing the fix
• Review and restrict access to the ReportIncident functionality to trusted user groups only
• Implement temporary rate limiting at the web server or reverse proxy level
• Monitor for exploitation attempts while preparing to deploy the patch

Patch Information

The vulnerability has been remediated on the master branch of the ReportIncident Extension. Administrators should update their MediaWiki installations to incorporate the latest version of the extension.

Patch details are available in the Wikimedia Code Change Log. Additional context and discussion can be found in the Wikimedia Task Discussion.

Workarounds

• Deploy rate limiting at the web server level (Apache mod_ratelimit, Nginx limit_req) to constrain request frequency
• Configure firewall rules to limit connections per source IP address
• Temporarily disable the ReportIncident Extension if not critical to operations
• Implement IP-based blocking for sources exhibiting abusive request patterns

# Nginx rate limiting configuration example for MediaWiki
limit_req_zone $binary_remote_addr zone=mediawiki_reportincident:10m rate=10r/m;

location /w/api.php {
    # Apply rate limiting to API endpoints
    limit_req zone=mediawiki_reportincident burst=5 nodelay;
    # Existing configuration continues below
}