CVE-2024-49363 in Misskey
Summary
by MITRE • 12/18/2024
Misskey is an open source, federated social media platform. In affected versions FileServerService (media proxy) in github.com/misskey-dev/misskey 2024.10.1 or earlier did not detect proxy loops, which allows remote actors to execute a self-propagating reflected/amplified distributed denial-of-service via a maliciously crafted note. FileServerService.prototype.proxyHandler did not check incoming requests are not coming from another proxy server. An attacker can execute an amplified denial-of-service by sending a nested proxy request to the server and end the request with a malicious redirect back to another nested proxy request. Leading to unbounded recursion until the original request is timed out. This issue has been addressed in version 2024.11.0-alpha.3. Users are advised to upgrade. Users unable to upgrade may configure the reverse proxy to block requests to the proxy with an empty User-Agent header or one containing Misskey/. An attacker can not effectively modify the User-Agent header without making another request to the server.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 02/17/2025
The vulnerability CVE-2024-49363 affects Misskey, an open source federated social media platform that enables decentralized communication across interconnected instances. This security flaw resides within the FileServerService component responsible for media proxy functionality, specifically in the proxyHandler method that processes incoming requests. The issue stems from insufficient validation mechanisms that fail to detect and prevent proxy loop conditions, creating a critical security gap in the platform's distributed architecture.
The technical implementation flaw occurs when the FileServerService.prototype.proxyHandler method lacks proper checks to identify whether incoming requests originate from another proxy server within the federation. This absence of validation creates a recursive loop condition where malicious actors can craft specially designed notes containing nested proxy requests. When the server processes these requests, it follows the redirect chain without termination checks, leading to unbounded recursion that consumes excessive system resources and processing power.
This vulnerability enables a self-propagating reflected/amplified distributed denial-of-service attack pattern that operates through federated network propagation. The attack mechanism involves an attacker sending a nested proxy request that ultimately ends with a malicious redirect back to another nested proxy request, creating an infinite loop of request processing. The recursive nature of this flaw continues until the original request times out, effectively exhausting server resources and rendering the service unavailable to legitimate users. This behavior aligns with attack patterns described in the ATT&CK framework under defensive evasion and denial of service techniques, specifically targeting infrastructure availability through resource exhaustion.
The operational impact of this vulnerability extends beyond simple service disruption to compromise the entire federated network ecosystem. When exploited, the vulnerability can cascade across multiple Misskey instances, amplifying the denial-of-service effect exponentially. The issue affects all versions of Misskey up to and including 2024.10.1, making a significant portion of the deployed user base vulnerable to coordinated attacks. The vulnerability's exploitation requires minimal technical skill but can cause substantial damage to network availability and user experience.
Mitigation strategies include upgrading to version 2024.11.0-alpha.3 where the issue has been resolved through proper proxy loop detection mechanisms. Organizations unable to immediately upgrade can implement reverse proxy configurations to block requests containing empty User-Agent headers or those with User-Agent strings containing "Misskey/". This workaround prevents exploitation by blocking the specific request patterns used in the attack, though it requires careful configuration to avoid blocking legitimate traffic. The solution addresses the underlying CWE-674 vulnerability category related to uncontrolled recursion in software systems, specifically targeting the lack of proper input validation and loop detection mechanisms. Security practitioners should implement monitoring for unusual proxy request patterns and establish automated alerting for potential exploitation attempts to maintain network resilience against similar future vulnerabilities.