_GitLab Plugin allows cross-channel post injection and phishing via missing channel permission checks in issue API endpoints_
Summary
| CVE | CVE-2026-16049 |
|---|---|
| State | PUBLISHED |
| Assigner | Mattermost |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-08-17 15:16:54 UTC |
| Updated | 2026-08-18 15:04:46 UTC |
| Description | Mattermost Plugins versions <=11.8 10.20.11 11.5.7.0 _The Mattermost GitLab plugin fails to verify channel permissions when processing API requests with a caller-supplied_ {{post_id}}_, and fails to validate the_ {{web_url}} _parameter against the configured GitLab instance, which allows an authenticated attacker to inject bot-authored messages containing arbitrary URLs into channels they do not have access to via the_ {{createIssue}} _and_ {{attachCommentToIssue}} _API endpoints._ Mattermost Advisory ID: MMSA-2026-00673 |
Risk And Classification
Primary CVSS: v3.1 4.3 MEDIUM from [email protected]
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
EPSS: 0.002180000 probability, percentile 0.124900000 (date 2026-08-18)
Problem Types: CWE-862 | CWE-862 CWE-862: Missing Authorization
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | [email protected] | Secondary | 4.3 | MEDIUM | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N |
| 3.1 | CNA | CVSS | 3.9 | LOW | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N |
CVSS v3.1 Breakdown
Attack Vector
NetworkAttack Complexity
LowPrivileges Required
LowUser Interaction
NoneScope
UnchangedConfidentiality
LowIntegrity
NoneAvailability
NoneCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Mattermost | Mattermost | affected 10.20.11 semver | Not specified |
| CNA | Mattermost | Mattermost | affected 11.5.7 semver | Not specified |
| CNA | Mattermost | Mattermost | unaffected 11.9.0 | Not specified |
| CNA | Mattermost | Mattermost | unaffected 10.11.21 | Not specified |
| CNA | Mattermost | Mattermost | unaffected 11.7.6 | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| mattermost.com/security-updates | [email protected] | mattermost.com | |
| 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: MindFlare007 (en)
Additional Advisory Data
Solutions
CNA: Update Mattermost Plugins to versions 11.9.0, 10.11.21, 11.7.6 or higher.
There are currently no legacy QID mappings associated with this CVE.