CVE-2026-19541— Outgoing OAuth connection client secret exposure during connection validation
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 版本 11.9.x（≤ 11.9.1）、11.8.x（≤ 11.8.5）、11.7.x（≤ 11.7.10）以及 11.10.x（≤ 11.10.1）在验证出站 OAuth 连接时，未强制要求重新输入已存储的客户端密钥（client secret）。这导致拥有管理出站 OAuth 连接权限的已认证用户，可通过将令牌 URL 指向攻击者控制的端点并触发验证流程，从而窃取该密钥。 Mattermost 安全公告编号：MMSA-2026-00761
Possible ATT&CK Techniques 1 AI
T1557 · Adversary-in-the-MiddleAffected Version Matrix 9
| Vendor | Product | Version Range | Status |
|---|---|---|---|
| Mattermost | Mattermost | 11.9.0≤ 11.9.1 |
affected |
11.8.0≤ 11.8.5 |
affected | ||
11.7.0≤ 11.7.10 |
affected | ||
11.10.0≤ 11.10.1 |
affected | ||
11.11.0 |
unaffected | ||
11.9.2 |
unaffected | ||
11.8.6 |
unaffected | ||
11.7.11 |
unaffected | ||
| … +1 more rows | |||
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I. Basic Information for CVE-2026-19541
Vulnerability Information
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Vulnerability Title
Outgoing OAuth connection client secret exposure during connection validation
Source: CVE Program / CVE List V5
Vulnerability Description
Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10, 11.10.x <= 11.10.1 fail to require re-entry of the stored client secret when validating an outgoing OAuth connection, which allows an authenticated user with permission to manage outgoing OAuth connections to obtain the secret via pointing the token URL at an attacker-controlled endpoint and triggering validation.. Mattermost Advisory ID: MMSA-2026-00761
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
通过发送数据的信息暴露
Source: CVE Program / CVE List V5
Affected Products
| Vendor | Product | Affected Versions | CPE | Subscribe |
|---|---|---|---|---|
| Mattermost | Mattermost | 11.9.0 ~ 11.9.1 | - |
|
II. Public POCs for CVE-2026-19541
| # | POC Description | Source Link | Shenlong Link |
|---|
AI-Generated POC
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Same Patch Batch · Mattermost · 2026-10-16 · 15 CVEs total
| CVE-2026-16453 | 7.1 HIGH | Mattermost SAML RelayState forgery allows unauthorized team membership |
| CVE-2026-18551 | 6.5 MEDIUM | Mattermost guest account privilege escalation via member roles API |
| CVE-2026-19621 | 6.5 MEDIUM | Mattermost leaks interactive-message integration secrets to non-admin users via post-delet |
| CVE-2026-16251 | 6.5 MEDIUM | Mattermost local image proxy allows server memory exhaustion via unbounded image response |
| CVE-2026-18795 | 6.4 MEDIUM | Missing server side validation allowed user to quarantine a DM and GM post |
| CVE-2026-18223 | 5.0 MEDIUM | Mattermost invitation tokens not bound to invited email address allowing unauthorized team |
| CVE-2026-19601 | 4.9 MEDIUM | Disclosure of AD/LDAP bind password via Test Connection |
| CVE-2026-19600 | 4.5 MEDIUM | Mattermost logs plaintext authentication tokens in debug-level server logs on failed auth |
| CVE-2026-19076 | 4.4 MEDIUM | Mattermost fails to reject OAuth application sessions in account type switch, allowing acc |
| CVE-2026-19603 | 4.3 MEDIUM | Private channel ID disclosure via user status endpoints |
| CVE-2026-19867 | 4.3 MEDIUM | Uncapped mention keys in user notification properties allow CPU exhaustion during post pro |
| CVE-2026-18560 | 4.3 MEDIUM | Improper order of authorisations in Mattermost GetFile API leads to an authenticated user |
| CVE-2026-18256 | 4.3 MEDIUM | Private team metadata disclosure via the team search API |
| CVE-2026-18799 | 4.3 MEDIUM | Mattermost Server fails to restrict Slack import account binding, allowing team admins to |
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Same weakness: CWE-201
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