CVE-2026-21388— Unbounded Request Body Read in MS Teams Plugin {{/lifecycle}} Webhook Endpoint
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 Plugins是美国Mattermost公司的一个插件，提供强大的功能延伸和与服务器和网络/桌面应用程序都紧密整合。 Mattermost Plugins 2.3.1及之前版本存在安全漏洞，该漏洞源于未能限制/lifecycle Webhook端点上的请求主体大小，可能导致经过身份验证的攻击者通过发送过大的JSON有效载荷引发内存耗尽和拒绝服务攻击。
Possible ATT&CK Techniques 1 AI
T1499 · Endpoint Denial of Service
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I. Basic Information for CVE-2026-21388
Vulnerability Information
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Vulnerability Title
Unbounded Request Body Read in MS Teams Plugin {{/lifecycle}} Webhook Endpoint
Source: CVE Program / CVE List V5
Vulnerability Description
Mattermost Plugins versions <=2.3.1 fail to limit the request body size on the {{/lifecycle}} webhook endpoint which allows an authenticated attacker to cause memory exhaustion and denial of service via sending an oversized JSON payload. Mattermost Advisory ID: MMSA-2026-00610
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
Source: CVE Program / CVE List V5
Vulnerability Type
不加限制或调节的资源分配
Source: CVE Program / CVE List V5
Vulnerability Title
Mattermost Plugins 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Mattermost Plugins是美国Mattermost公司的一个插件，提供强大的功能延伸和与服务器和网络/桌面应用程序都紧密整合。 Mattermost Plugins 2.3.1及之前版本存在安全漏洞，该漏洞源于未能限制/lifecycle Webhook端点上的请求主体大小，可能导致经过身份验证的攻击者通过发送过大的JSON有效载荷引发内存耗尽和拒绝服务攻击。
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 ~ 2.3.1 | - |
|
II. Public POCs for CVE-2026-21388
| # | POC Description | Source Link | Shenlong Link |
|---|
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V. Comments for CVE-2026-21388
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