CVE-2026-14298 in Mattermost
Summary
by MITRE • 08/13/2026
Mattermost versions 11.9.x <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.7, 10.11.x <= 10.11.22 fail to properly limit resource consumption when processing certain user-supplied input, which allows an authenticated user to cause a denial of service. Mattermost Advisory ID: MMSA-2026-00713
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Analysis
by VulDB Data Team • 08/13/2026
This vulnerability represents a critical resource exhaustion flaw in Mattermost messaging platform versions spanning multiple release branches including 11.9.0, 11.8.4, 11.7.7, and 10.11.22. The issue stems from inadequate input validation mechanisms that fail to properly constrain resource consumption during processing of user-supplied data, creating a pathway for authenticated attackers to deliberately consume system resources and induce denial of service conditions. The vulnerability specifically manifests when the application processes certain types of user input that trigger excessive memory allocation or CPU usage patterns without proper rate limiting or size constraints.
The technical implementation of this flaw involves insufficient bounds checking and resource management within the application's input processing pipeline. When authenticated users submit maliciously crafted payloads, the system fails to implement adequate safeguards against resource-intensive operations that could lead to memory exhaustion or excessive computational overhead. This type of vulnerability aligns with CWE-770, which addresses allocation of resources without proper limits, and falls under the broader category of resource exhaustion attacks that can severely impact system availability and performance. The flaw operates at the application layer where user input is processed and validated, making it particularly dangerous as it requires only authenticated access to exploit.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the entire messaging infrastructure. An attacker with valid credentials could systematically consume available memory, CPU cycles, or other system resources to make the Mattermost instance unavailable to legitimate users. This denial of service condition could affect collaboration workflows, communication channels, and overall platform reliability for organizations relying on Mattermost for team communications. The vulnerability affects multiple version lines, indicating a persistent issue in the codebase that has not been adequately addressed across different release branches, suggesting potential architectural problems in resource management patterns.
Organizations should implement immediate mitigations including enhanced input validation controls, rate limiting mechanisms, and monitoring systems to detect unusual resource consumption patterns. The recommended approach involves configuring proper bounds checking for all user-supplied inputs, implementing automated resource usage alerts, and ensuring that system administrators can quickly identify and respond to abnormal processing behavior. Security teams should also consider deploying network-level protections such as traffic shaping or connection limiting to prevent exploitation attempts. This vulnerability demonstrates the importance of robust resource management practices in web applications and aligns with ATT&CK technique T1499.004, which covers network denial of service attacks through resource exhaustion. Organizations must prioritize patching affected versions while implementing defensive measures to protect against similar vulnerabilities in their infrastructure.