CVE-2026-6517— Mattermost Desktop App fails to restrict the allow list of domains which NTLM credentials are passed
Possible ATT&CK Techniques 1AI
T1005 · Data from Local SystemAffected Version Matrix 3
| Vendor | Product | Version Range | Status |
|---|---|---|---|
| Mattermost | Mattermost | ≤ 5.5.13 | affected |
6.2.0 | unaffected | ||
5.13.6.0 | unaffected |
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I. Basic Information for CVE-2026-6517
Vulnerability Information
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Vulnerability Title
Mattermost Desktop App fails to restrict the allow list of domains which NTLM credentials are passed
Source: NVD (National Vulnerability Database)
Vulnerability Description
Mattermost Desktop App versions <=6.1 5.5.13.0 fail to restrict the allow list of domains to which NTLM credentials were forwarded to in the Mattermost Desktop App which allows any user on a server without the image proxy enabled to intercept other users credentials via embedding an image that routes to an external web server. Mattermost Advisory ID: MMSA-2026-00651
Source: NVD (National Vulnerability Database)
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N
Source: NVD (National Vulnerability Database)
Vulnerability Type
不充分的凭证保护机制
Source: NVD (National Vulnerability Database)
Vulnerability Title
Mattermost 信任管理问题漏洞
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 6.1 5.5.13.0及之前版本存在信任管理问题漏洞，该漏洞源于未能限制允许NTLM凭据转发的域名白名单，可能导致任何未启用图像代理的服务器上的用户通过嵌入路由到外部Web服务器的图像来拦截其他用户的凭据。
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 ~ 5.5.13 | - |
II. Public POCs for CVE-2026-6517
| # | POC Description | Source Link | Shenlong Link |
|---|
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IV. Related Vulnerabilities
Same product: Mattermost
- CVE-2026-6541
Unscoped updates to other playbooks' metric configuration - CVE-2026-9820
Mattermost schemes teams endpoint exposes private team invit - CVE-2026-9824
Remote cluster metadata enumeration via /share-channel autoc - CVE-2026-9597
Deactivated guest accounts can authenticate via magic-link t - CVE-2026-6850
Crafted message attachment causes client-side denial of serv
Same vendor: Mattermost
- CVE-2026-6541
Unscoped updates to other playbooks' metric configuration - CVE-2026-9820
Mattermost schemes teams endpoint exposes private team invit - CVE-2026-9824
Remote cluster metadata enumeration via /share-channel autoc - CVE-2026-9597
Deactivated guest accounts can authenticate via magic-link t - CVE-2026-6850
Crafted message attachment causes client-side denial of serv
Same weakness: CWE-522
- CVE-2026-48295
CAI Content Credentials | Insufficiently Protected Credentia - CVE-2026-47282
GitHub Copilot and Visual Studio Code Information Disclosure - CVE-2026-59891
Credential confusion in @sigstore/oci can leak registry cr - CVE-2026-59209
n8n: Shared Credential Header Leak via HTTP Request Paginati - CVE-2026-11827
Insufficiently Protected Credentials in GitLab
V. Comments for CVE-2026-6517
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