Denial of Service Vulnerability in Mattermost by Mattermost
CVE-2026-10819

6.5MEDIUM

Key Information:

Vendor

Mattermost
Status
Mattermost
Vendor
CVE Published:
27 July 2026

What is CVE-2026-10819?

Mattermost versions up to 11.6.5, 10.11.20, 11.8.1, and 11.7.4 are susceptible to a denial of service attack due to inadequate restriction on the number of frames and file size for animated GIF uploads. An authenticated attacker could exploit this by uploading a specially crafted animated GIF as a custom emoji, leading to potential service disruptions for users. The vulnerabilities highlighted emphasize the need for robust input validation and security measures in messaging platforms.

Affected Version(s)

Mattermost 11.6.0 <= 11.6.5

Mattermost 10.11.0 <= 10.11.20

Mattermost 11.8.0 <= 11.8.1

References

https://mattermost.com/security-updates
vendor-advisory

CVSS V3.1

Score:
6.5
Severity:
MEDIUM
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
Low
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Adam Korczynski
.