CVE-2026-16049— _GitLab Plugin allows cross-channel post injection and phishing via missing channel permission checks in issue API endpoints_
Possible ATT&CK Techniques 1AI
T1190 · Exploit Public-Facing ApplicationAffected Version Matrix 5
| Vendor | Product | Version Range | Status |
|---|---|---|---|
| Mattermost | Mattermost | ≤ 10.20.11 | affected |
≤ 11.5.7 | affected | ||
11.9.0 | unaffected | ||
10.11.21 | unaffected | ||
11.7.6 | unaffected |
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I. Basic Information for CVE-2026-16049
Vulnerability Information
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Vulnerability Title
_GitLab Plugin allows cross-channel post injection and phishing via missing channel permission checks in issue API endpoints_
Source: CVE Program / CVE List V5
Vulnerability 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
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
授权机制缺失
Source: CVE Program / CVE List V5
Vulnerability Title
Mattermost 授权问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Mattermost是美国Mattermost公司开源的一个开源协作平台。 Mattermost 10.20.11及之前版本和11.5.7及之前版本存在授权问题漏洞，该漏洞源于在处理API请求时未验证调用方提供的post_id对应的频道权限，且未验证web_url参数，可能导致经过身份验证的攻击者通过createIssue和attachCommentToIssue API端点向无权访问的频道注入包含任意URL的机器人消息。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)
Affected Products
| Vendor | Product | Affected Versions | CPE | Subscribe |
|---|---|---|---|---|
| Mattermost | Mattermost | 0 ~ 10.20.11 | - |
II. Public POCs for CVE-2026-16049
| # | POC Description | Source Link | Shenlong Link |
|---|
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Same Patch Batch · Mattermost · 2026-08-17 · 13 CVEs total
| CVE-2026-9816 | 8.3 HIGH | Insufficient server-side validation of board member role fields permits privilege escalati |
| CVE-2026-9859 | 6.5 MEDIUM | Mattermost Boards plugin didn’t enforce role-based authorization on board channel link all |
| CVE-2026-10080 | 6.5 MEDIUM | Boards plugin panics on WebSocket command with non-string field types |
| CVE-2026-10527 | 6.3 MEDIUM | Boards plugin retains Board Admin rights for users demoted to System Guest |
| CVE-2026-16048 | 6.3 MEDIUM | Channel member roles accept out-of-scope roles |
| CVE-2026-16047 | 4.3 MEDIUM | Board channel linking without read channel permission validation |
| CVE-2026-15754 | 4.2 MEDIUM | Missing per-channel team-scope check in ABAC access control policy unassign allows cross-t |
| CVE-2026-16044 | 3.9 LOW | Insufficient validation of guest board admin privileges on archive import |
| CVE-2026-75587 | 3.6 LOW | Plaintext pre-auth secret exposure via Desktop App diagnostics report |
| CVE-2026-9693 | 3.5 LOW | Mattermost thread memberships persist after team removal, exposing private channel thread |
| CVE-2026-16046 | 3.5 LOW | Missing run-state validation on finished playbook runs |
| CVE-2026-16045 | 2.7 LOW | Delegated OAuth tokens could revoke unrelated OAuth application authorizations |
IV. Related Vulnerabilities
Same product: Mattermost
- CVE-2026-75587
Plaintext pre-auth secret exposure via Desktop App diagnosti - CVE-2026-9693
Mattermost thread memberships persist after team removal, ex - CVE-2026-9859
Mattermost Boards plugin didn’t enforce role-based authoriza - CVE-2026-9816
Insufficient server-side validation of board member role fie - CVE-2026-10080
Boards plugin panics on WebSocket command with non-string fi
Same vendor: Mattermost
- CVE-2026-75587
Plaintext pre-auth secret exposure via Desktop App diagnosti - CVE-2026-9693
Mattermost thread memberships persist after team removal, ex - CVE-2026-9859
Mattermost Boards plugin didn’t enforce role-based authoriza - CVE-2026-9816
Insufficient server-side validation of board member role fie - CVE-2026-10080
Boards plugin panics on WebSocket command with non-string fi
Same weakness: CWE-862
- CVE-2026-75866
Punk::OAuth2::Server versions through 0.03 for Perl issue ac - CVE-2026-5093
Greenshift <= 12.8.9 - Authenticated (Contributor+) Theme Se - CVE-2026-4244
Post Duplicator <= 3.0.11 - Missing Authorization to Authent - CVE-2026-12710
Missing Authorization in Application Integration QueryEngine - CVE-2026-75027
Themify Builder <= 7.8.0 - Missing Authorization to Unauthen
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