Medium severity · published Jul 27, 2026
CVE-2026-10819
Mattermost Server Denial of Service via Animated GIF Emoji Upload
6.5
CVSS
0.4%
EPSS
No
On KEV
Description
Mattermost versions 11.6.x <= 11.6.5, 10.11.x <= 10.11.20, 11.8.x <= 11.8.1, 11.7.x <= 11.7.4 fail to limit the number of frames and enforce the file size cap on animated GIF uploads, which allows an authenticated attacker to cause a denial of service via a crafted animated GIF uploaded as a custom emoji.. Mattermost Advisory ID: MMSA-2026-00695
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 36% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
MA
Mattermost · Mattermost
11.6.0 through 11.6.5; 10.11.0 through 10.11.20; 11.8.0 through 11.8.1; 11.7.0 through 11.7.4 · source: vendor
MS
Mattermost Server · Mattermost
10.11.0 before 10.11.21; 11.6.0 before 11.6.6; 11.7.0 before 11.7.5; 11.8.0 before 11.8.2 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-10819
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-10819
Vendor Advisory
https://mattermost.com/security-updates
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