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. Fetching posts with huge amounts of reactions results in Uncontrolled Resource Consumption.
{
    "github_reviewed_at": "2024-02-09T21:35:00Z",
    "severity": "MODERATE",
    "github_reviewed": true,
    "cwe_ids": [
        "CWE-400"
    ],
    "nvd_published_at": "2024-02-09T16:15:07Z"
}