title: Denial of service in mattermost mobile apps and server via emoji reactions
description: 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.
problem types: CWE-400: Uncontrolled Resource Consumption
affected:
{
defaultStatus: unaffected
product: Mattermost
vendor: Mattermost
versions:
lessThanOrEqual: 8.1.7, status: affected, version: 0, versionType: semver
lessThanOrEqual: 9.1.4, status: affected, version: 0, versionType: semver
lessThanOrEqual: 9.2.3, status: affected, version: 0, versionType: semver
status: unaffected, version: 9.3.0
status: unaffected, version: 9.2.4
status: unaffected, version: 9.1.5
status: unaffected, version: 8.1.8
}
metrics:
cvssV3_1: [
attackComplexity: LOW
attackVector: NETWORK
availabilityImpact: LOW
baseScore: 4.3
baseSeverity: MEDIUM
confidentialityImpact: NONE
integrityImpact: NONE
privilegesRequired: LOW
scope: UNCHANGED
userInteraction: NONE
vectorString: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
version: 3.1
]
format: CVSS
scenarios: GENERAL
solutions: Update Mattermost Server to versions 9.3.0, 9.2.4, 9.1.5, 8.1.8 or higher.