CVE-2026-96259— Mattermost server-side request forgery via OAuth endpoints configurable by a System Administrator
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 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 apply the internal-connection filter to OAuth endpoint requests, which allows a System Administrator to make the server issue requests to internal network add
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I. Basic Information for CVE-2026-96259
Vulnerability Information
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Vulnerability Title
Mattermost server-side request forgery via OAuth endpoints configurable by a System Administrator
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 apply the internal-connection filter to OAuth endpoint requests, which allows a System Administrator to make the server issue requests to internal network addresses and read the responses via the configured OAuth token and userinfo endpoints.. Mattermost Advisory ID: MMSA-2026-00776
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
服务端请求伪造(SSRF)
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-2026-96259
| # | POC Description | Source Link | Shenlong Link |
|---|
AI-Generated POC
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Same Patch Batch · Mattermost · 2026-09-22 · 3 CVEs total
| CVE-2026-96260 | 6.5 MEDIUM | Mattermost server missing request body size limit on plugin routes allows denial of servic |
| CVE-2026-95666 | 4.3 MEDIUM | Unbounded post ID array in the bulk reactions endpoint allows denial of service |
IV. Related Vulnerabilities
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CVE-2026-96260
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CVE-2026-95666
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CVE-2026-95666
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CVE-2026-75588
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Same weakness: CWE-918
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V. Comments for CVE-2026-96259
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