CVE-2021-37863 in Mattermost
Summary
by MITRE • 12/17/2021
Mattermost 6.0 and earlier fails to sufficiently validate parameters during post creation, which allows authenticated attackers to cause a client-side crash of the web application via a maliciously crafted post.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 03/20/2023
The vulnerability identified as CVE-2021-37863 represents a critical client-side input validation flaw within Mattermost version 6.0 and earlier systems. This issue stems from insufficient parameter validation during the post creation process, creating a pathway for authenticated attackers to exploit the platform's web application interface. The flaw specifically targets the manner in which the system handles user-generated content, particularly when processing posts that contain maliciously crafted parameters. Security researchers have classified this vulnerability as a client-side crash condition that can be triggered through carefully constructed post content, potentially disrupting normal application operations and user experience.
The technical execution of this vulnerability involves an attacker leveraging their authenticated access to manipulate post creation parameters in ways that bypass existing validation mechanisms. When the web application processes these malformed parameters, it fails to properly sanitize or validate the input before rendering the content, leading to a crash condition that affects the client-side browser environment. This type of vulnerability falls under the category of improper input validation as defined by CWE-20, which specifically addresses issues where applications fail to properly validate or sanitize input data. The vulnerability demonstrates a clear breakdown in the application's defense-in-depth strategy, as it allows an authenticated user to escalate their privileges from normal user access to a position where they can disrupt application availability.
From an operational impact perspective, this vulnerability creates significant risk for organizations relying on Mattermost for collaboration and communication. The client-side crash capability means that attackers can potentially disrupt the work environment for multiple users simultaneously, as the affected web application becomes unavailable or unstable for those accessing the platform. The authenticated nature of the attack requires attackers to already have valid credentials, but this does not mitigate the risk since compromised accounts can lead to broader system compromise. The vulnerability also aligns with ATT&CK technique T1210, which involves exploiting weaknesses in the application or system to gain unauthorized access or cause denial of service conditions. Organizations using Mattermost may experience reduced productivity, communication disruption, and potential escalation to more serious security incidents if attackers leverage this vulnerability to gain further access to the system.
The recommended mitigation strategy involves immediate deployment of the patched version of Mattermost that addresses the input validation flaw in post creation functionality. Organizations should also implement additional monitoring for unusual post creation patterns that might indicate exploitation attempts, as well as ensure that all user accounts maintain strong authentication controls. Security teams should conduct thorough vulnerability assessments to identify any other potential input validation weaknesses within the application's user interface components. The fix typically involves implementing comprehensive parameter validation that sanitizes all user input before processing and rendering, ensuring that malformed or malicious parameters are rejected before they can cause system instability. Additionally, organizations should consider implementing rate limiting and content filtering mechanisms to further protect against abuse of the post creation functionality while maintaining the platform's usability for legitimate users.