CVE-2026-9708— Incoming webhook user attribution via unvalidated webhook owner
Quick assessment
Affected
Mattermost Mattermost
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.
Mattermost是美国Mattermost公司开源的一个开源协作平台。 Mattermost 11.7.x及之前的11.7.2版本、11.6.x及之前的11.6.4版本、10.11.x及之前的10.11.19版本存在授权问题漏洞，该漏洞源于未验证指定的传入webhook用户是否有权访问目标团队或频道，导致具有webhook管理权限的请求者可以通过特制的传入webhook配置和有效载荷创建归属于其他用户的消息或直接消息。
Possible ATT&CK Techniques 1 AI
T1134 · Access Token ManipulationAffected Version Matrix 7
| Vendor | Product | Version Range | Status |
|---|---|---|---|
| Mattermost | Mattermost | 11.7.0≤ 11.7.2 |
affected |
11.6.0≤ 11.6.4 |
affected | ||
10.11.0≤ 10.11.19 |
affected | ||
11.8.0 |
unaffected | ||
11.7.3 |
unaffected | ||
11.6.5 |
unaffected | ||
10.11.20 |
unaffected |
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I. Basic Information for CVE-2026-9708
Vulnerability Information
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Vulnerability Title
Incoming webhook user attribution via unvalidated webhook owner
Source: CVE Program / CVE List V5
Vulnerability Description
Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4, 10.11.x <= 10.11.19 fail to validate that an assigned incoming webhook user has access to the target team or channel, which allows a requester with webhook management permissions to create posts or direct messages attributed to another user via crafted incoming webhook configuration and payloads.. Mattermost Advisory ID: MMSA-2026-00683
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
通过用户控制密钥绕过授权机制
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 11.7.x及之前的11.7.2版本、11.6.x及之前的11.6.4版本、10.11.x及之前的10.11.19版本存在授权问题漏洞，该漏洞源于未验证指定的传入webhook用户是否有权访问目标团队或频道，导致具有webhook管理权限的请求者可以通过特制的传入webhook配置和有效载荷创建归属于其他用户的消息或直接消息。
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 | 11.7.0 ~ 11.7.2 | - |
|
II. Public POCs for CVE-2026-9708
| # | POC Description | Source Link | Shenlong Link |
|---|
AI-Generated POC
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Same Patch Batch · Mattermost · 2026-07-13 · 10 CVEs total
| CVE-2026-6850 | 6.5 MEDIUM | Crafted message attachment causes client-side denial of service via markdown parser regex |
| CVE-2026-10106 | 6.5 MEDIUM | Unauthorized users can trigger interactive post actions in private channels via action coo |
| CVE-2026-9571 | 5.9 MEDIUM | Deactivated user accounts can continue to obtain valid OAuth access tokens via refresh tok |
| CVE-2026-9597 | 5.4 MEDIUM | Deactivated guest accounts can authenticate via magic-link token in Mattermost REST API lo |
| CVE-2026-10085 | 5.4 MEDIUM | Ordinary group/direct message member can enable group_constrained and remove all channel p |
| CVE-2026-6541 | 4.3 MEDIUM | Unscoped updates to other playbooks' metric configuration |
| CVE-2026-9824 | 4.3 MEDIUM | Remote cluster metadata enumeration via /share-channel autocomplete |
| CVE-2026-10103 | 4.3 MEDIUM | Authenticated remote cluster can modify or delete posts it does not own in Mattermost Conn |
| CVE-2026-9820 | 3.8 LOW | Mattermost schemes teams endpoint exposes private team invite IDs |
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