Mattermost Server Denial of Service via Animated GIF Emoji Upload
Summary
| CVE | CVE-2026-10819 |
|---|---|
| State | PUBLISHED |
| Assigner | Mattermost |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-07-27 15:16:46 UTC |
| Updated | 2026-08-03 15:23:50 UTC |
| 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 |
Risk And Classification
Primary CVSS: v3.1 6.5 MEDIUM from [email protected]
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
EPSS: 0.002350000 probability, percentile 0.145300000 (date 2026-07-29)
Problem Types: CWE-409 | CWE-409 CWE-409: Improper Handling of Highly Compressed Data (Data Amplification)
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | [email protected] | Secondary | 6.5 | MEDIUM | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H |
| 3.1 | CNA | CVSS | 6.5 | MEDIUM | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H |
CVSS v3.1 Breakdown
Attack Vector
NetworkAttack Complexity
LowPrivileges Required
LowUser Interaction
NoneScope
UnchangedConfidentiality
NoneIntegrity
NoneAvailability
HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
NVD Known Affected Configurations (CPE 2.3)
| Type | Vendor | Product | Version | Update | Edition | Language |
|---|---|---|---|---|---|---|
| Application | Mattermost | Mattermost Server | All | All | All | All |
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Mattermost | Mattermost | affected 11.6.0 11.6.5 semver | Not specified |
| CNA | Mattermost | Mattermost | affected 10.11.0 10.11.20 semver | Not specified |
| CNA | Mattermost | Mattermost | affected 11.8.0 11.8.1 semver | Not specified |
| CNA | Mattermost | Mattermost | affected 11.7.0 11.7.4 semver | Not specified |
| CNA | Mattermost | Mattermost | unaffected 11.9.0 | Not specified |
| CNA | Mattermost | Mattermost | unaffected 11.6.6 | Not specified |
| CNA | Mattermost | Mattermost | unaffected 10.11.21 | Not specified |
| CNA | Mattermost | Mattermost | unaffected 11.8.2 | Not specified |
| CNA | Mattermost | Mattermost | unaffected 11.7.5 | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| mattermost.com/security-updates | [email protected] | mattermost.com | Vendor Advisory |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Adam Korczynski (en)
Additional Advisory Data
Solutions
CNA: Update Mattermost to versions 11.9.0, 11.6.6, 10.11.21, 11.8.2, 11.7.5 or higher.
There are currently no legacy QID mappings associated with this CVE.