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TI-2026-09287 Aliases CVE-2026-10819GHSA-qf49-6jm2-h67m

Mattermost Server Denial of Service via Animated GIF Emoji Upload

Priority LOW 29CWE-409Published · Updated

Key facts

Attack vector
Network
Privileges required
Low
User interaction
None
Attack complexity
Low
Impact type
—
Confidentiality · integrity · availability
None · None · High
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA.

Summary

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

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.0042 36th percentileScored 2026-11-07
Fix Fixed Mattermost (Mattermost): 11.9.0, 11.6.6, 10.11.21 +2

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
MattermostMattermost11.6.0 – 11.6.5; 10.11.0 – 10.11.20; 11.8.0 – 11.8.1; 11.7.0 – 11.7.411.9.0, 11.6.6, 10.11.21, 11.8.2, 11.7.5Patch availableCNA
  • Mattermost VendorMattermost Affected 11.6.0 – 11.6.5; 10.11.0 – 10.11.20; 11.8.0 – 11.8.1; 11.7.0 – 11.7.4 Fixed in 11.9.0, 11.6.6, 10.11.21, 11.8.2, 11.7.5 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*10.11.0 to before 10.11.21; 11.6.0 to before 11.6.6; 11.7.0 to before 11.7.5; 11.8.0 to before 11.8.2VulnerableMattermost
  • cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* Versions 10.11.0 to before 10.11.21; 11.6.0 to before 11.6.6; 11.7.0 to before 11.7.5; 11.8.0 to before 11.8.2 Vulnerable ·Mattermost

Remediation

  • Fix · CNA Mattermost (Mattermost) Fixed in 11.9.0, 11.6.6, 10.11.21, 11.8.2, 11.7.5

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-10819
  2. 2026-10-03 Alias added: GHSA-qf49-6jm2-h67m

References

Advisory 1

  • TI-2025-18933 Arbitrary file read in Mattermost Boards via import & export board archive CVSS 3.1CRITICAL 9.9
  • TI-2025-04465 Path Traversal Leading to RCE by Any Authenticated Mattermost User CVSS 3.1CRITICAL 9.9
  • TI-2017-14068 An issue was discovered in Mattermost Server before 3.6.2. CVSS 3.1CRITICAL 9.8
  • TI-2017-14060 An issue was discovered in Mattermost Server before 3.8.2, 3.7.5, and 3.6.7. CVSS 3.1CRITICAL 9.8
  • TI-2017-14048 An issue was discovered in Mattermost Server before 4.1.0, 4.0.4, and 3.10.3. CVSS 3.1CRITICAL 9.8
  • TI-2025-14360 Arbitrary file read via block duplication in Mattermost Boards CVSS 3.1CRITICAL 9.9
See all 505 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences