CVE-2026-10819

Mattermost Server Denial of Service via Animated GIF Emoji Upload

State: Published
Severity: 6.5 Medium
Published: Jul 27, 2026
Updated: Jul 27, 2026
Reserved: Jun 4, 2026

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

Scores

CVSS	Score	Vector	Source
3.1	6.5 Medium	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H	Mattermost

Weaknesses

CWE-409 Improper Handling of Highly Compressed Data (Data Amplification)

Affected Products

Product	Versions
MattermostMattermost	11.6.0 through 11.6.5Affected 10.11.0 through 10.11.20Affected 11.8.0 through 11.8.1Affected 11.7.0 through 11.7.4Affected 11.9.0Not affected 11.6.6Not affected 10.11.21Not affected 11.8.2Not affected 11.7.5Not affected

References

MMSA-2026-00695vendor-advisory

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