Uncontrolled Resource Consumption Affecting github.com/mattermost/mattermost/server/v8/channels/app package, versions <8.1.8 >=9.0.0 <9.1.5-rc1 >=9.0.0 <9.2.4-rc1

Affected versions of this package are vulnerable to Uncontrolled Resource Consumption due to the application's failure to validate the existence of custom emoji reactions when appended to a post and its inability to restrict the quantity of custom emoji that can be added to a single post. An attacker can cause the mobile application to crash by sending a large number of non-existent custom emoji to a post.

Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its intended and legitimate users.

Unlike other vulnerabilities, DoS attacks usually do not aim at breaching security. Rather, they are focused on making websites and services unavailable to genuine users resulting in downtime.

One popular Denial of Service vulnerability is DDoS (a Distributed Denial of Service), an attack that attempts to clog network pipes to the system by generating a large volume of traffic from many machines.

When it comes to open source libraries, DoS vulnerabilities allow attackers to trigger such a crash or crippling of the service by using a flaw either in the application code or from the use of open source libraries.

Two common types of DoS vulnerabilities:

• High CPU/Memory Consumption- An attacker sending crafted requests that could cause the system to take a disproportionate amount of time to process. For example, commons-fileupload:commons-fileupload.

• Crash - An attacker sending crafted requests that could cause the system to crash. For Example, npm ws package

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