CVE-2026-16049
_GitLab Plugin allows cross-channel post injection and phishing via missing channel permission checks in issue API endpoints_
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
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- Low
- User interaction
- None
What an attacker can affect
- Confidentiality
- Low
- Integrity
- None
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
_GitLab Plugin allows cross-channel post injection and phishing via missing channel permission checks in issue API endpoints_
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
- Record
CVE-2026-16049- CVSS 3.1
- 3.9 Low
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N - Weakness
- CWE-862
- Updated
- 2026-11-02
EUVDEUVD-2026-60209
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
- Record
EUVD-2026-60209- CVSS 3.1
- 3.9 Low
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-vr3j-2q9w-h26r
Mattermost Plugins versions <=11.8 10.20.11 11.5.7.0 _The Mattermost GitLab plugin fails to...
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
- Record
GHSA-vr3j-2q9w-h26r- CVSS 3.1
- 4.3 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N - Weakness
- CWE-862
- Updated
- 2026-11-02
NVD
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
- Record
CVE-2026-16049- CVSS 3.1
- 4.3 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N - Weakness
- CWE-862
- Updated
- 2026-11-02
Affected products
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, GitHub Advisories, NVD |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-16049 is a low vulnerability (CVSS 3.9) in Mattermost, published August 17, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.29%, the 22nd percentile. No source names a fixed version.