CVE-2025-20621— Webapp crash via object that can't be cast to String in Attachment Field
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公司的一个开源协作平台。 Mattermost存在安全漏洞，该漏洞源于无法正确处理带有附件的帖子，允许攻击者通过创建此类帖子并将其发送到频道来导致Web应用崩溃。
Possible ATT&CK Techniques 1 AI
T1499 · Endpoint Denial of Service
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I. Basic Information for CVE-2025-20621
Vulnerability Information
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Vulnerability Title
Webapp crash via object that can't be cast to String in Attachment Field
Source: CVE Program / CVE List V5
Vulnerability Description
Mattermost versions 10.2.x <= 10.2.0, 9.11.x <= 9.11.5, 10.0.x <= 10.0.3, 10.1.x <= 10.1.3 fail to properly handle posts with attachments containing fields that cannot be cast to a String, which allows an attacker to cause the webapp to crash via creating and sending such a post to a channel.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
CWE-1287
Source: CVE Program / CVE List V5
Vulnerability Title
Mattermost 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Mattermost是美国Mattermost公司的一个开源协作平台。 Mattermost存在安全漏洞，该漏洞源于无法正确处理带有附件的帖子，允许攻击者通过创建此类帖子并将其发送到频道来导致Web应用崩溃。
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 | 10.2.0 ~ 10.2.0 | - |
|
II. Public POCs for CVE-2025-20621
| # | POC Description | Source Link | Shenlong Link |
|---|
AI-Generated POC
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Same Patch Batch · Mattermost · 2025-01-16 · 3 CVEs total
| CVE-2025-20630 | 6.5 MEDIUM | Mobile crash via object that can't be cast to String in Attachment Field |
| CVE-2025-20072 | 6.5 MEDIUM | Mobile crash via improper validation of proto style in attachments |
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V. Comments for CVE-2025-20621
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