CVE-2024-1402 in Mattermost
Summary
by MITRE • 02/09/2024
Mattermost fails to check if a custom emoji reaction exists when sending it to a post and to limit the amount of custom emojis allowed to be added in a post, allowing an attacker sending a huge amount of non-existent custom emojis in a post to crash the mobile app of a user seeing the post.
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Analysis
by VulDB Data Team • 03/03/2024
The vulnerability identified as CVE-2024-1402 represents a critical flaw in the Mattermost communication platform that stems from inadequate input validation and resource management within the emoji reaction handling mechanism. This issue specifically affects the mobile application client where users encounter a crash when viewing posts containing excessive custom emoji reactions. The root cause lies in the absence of proper validation checks that should verify the existence of custom emojis before processing them, combined with a lack of rate limiting or caps on the number of custom emojis that can be associated with a single post. This design oversight creates a potential denial of service condition that can be exploited through carefully crafted malicious posts.
The technical exploitation of this vulnerability occurs when an attacker constructs a post containing an excessive number of non-existent custom emoji reactions, typically in the range of hundreds or thousands of entries. The mobile application client processes each emoji reaction without first validating its existence in the system's emoji database, leading to a resource exhaustion scenario where the application attempts to handle invalid emoji references. This processing failure manifests as an application crash or unresponsive state when legitimate users attempt to view the malicious post, effectively disrupting normal communication workflows. The vulnerability operates at the application layer and specifically targets the mobile client implementation rather than server-side components.
From an operational impact perspective, this vulnerability undermines the reliability and availability of Mattermost mobile applications, creating a significant disruption to user experience and potentially affecting organizational communication. The crash condition affects all users viewing the malicious post regardless of their role or privileges within the system, making it a particularly dangerous vector for widespread disruption. Security practitioners should note that this vulnerability aligns with CWE-129, which addresses improper validation of input, and CWE-400, which covers resource exhaustion conditions. The attack pattern follows the ATT&CK technique T1499.004 for network denial of service, specifically targeting application availability through client-side exploitation.
Mitigation strategies should focus on implementing comprehensive input validation mechanisms that verify emoji existence before processing, establishing reasonable limits on custom emoji counts per post, and deploying defensive programming practices to prevent resource exhaustion. Organizations should consider implementing rate limiting for emoji reactions, validating all emoji references against the system's emoji database, and potentially introducing client-side sanitization of emoji inputs. Additionally, regular updates to Mattermost software should be prioritized to ensure patched versions are deployed, while monitoring systems should be configured to detect unusual emoji reaction patterns that might indicate exploitation attempts. The vulnerability demonstrates the importance of proper defensive programming practices and input validation in preventing resource exhaustion attacks that can compromise application availability.