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CVE-2026-16889— Stored XSS via Pre-Login Notice Image Upload Serves Attacker HTML from Application Origin

Quick assessment

Affected
Apereo Foundation openEQUELLA
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.

在 openEQUELLA 2026.1 之前的版本中，登录前通知图片上传接口（PUT /api/preloginnotice/image/{name}）未对上传文件的类型进行验证，而是根据提供的文件名动态生成 Content-Type 响应头。拥有 EDIT_SYSTEM_SETTINGS 权限的用户可上传 HTML 文件，该文件随后会以 text/html 类型从 openEQUELLA 源站返回，从而导致存储型跨站脚本（Stored XSS）漏洞。若 EDIT_SYSTEM_SETTINGS 权限已授予访客用

CVSS 4.8 · Medium

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application
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I. Basic Information for CVE-2026-16889

Vulnerability Information
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Vulnerability Title
Stored XSS via Pre-Login Notice Image Upload Serves Attacker HTML from Application Origin
Source: CVE Program / CVE List V5
Vulnerability Description
In openEQUELLA before 2026.1, the pre-login notice image upload endpoint (PUT /api/preloginnotice/image/{name}) does not validate the type of uploaded files and serves them with a Content-Type derived from the supplied filename. A user holding the EDIT_SYSTEM_SETTINGS permission can upload an HTML file that is then served as text/html from the openEQUELLA origin, resulting in stored cross-site scripting. Unauthenticated exploitation is possible where EDIT_SYSTEM_SETTINGS has been granted to the guest user or everyone.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
危险类型文件的不加限制上传
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Apereo Foundation openEQUELLA 2019.1 ~ 2026.1 -

II. Public POCs for CVE-2026-16889

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III. Intelligence Information for CVE-2026-16889

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Other References for CVE-2026-16889 (2)

Same Patch Batch · Apereo Foundation · 2026-10-29 · 6 CVEs total

CVE-2026-66088 9.4 CRITICAL Unrestricted Command Execution via system.execute
CVE-2026-66090 7.1 HIGH XML External Entity (XXE) Injection in Metadata Field Allows Arbitrary File Read
CVE-2026-66091 6.9 MEDIUM Unauthenticated IDOR Enables Disclosure of Other Users’ last-known details
CVE-2026-66089 6.1 MEDIUM XML External Entity (XXE) Vulnerability in SOAP Interface Allows External Entity Expansion
CVE-2026-66092 4.8 MEDIUM Stored XSS in pre-login notice via reachable legacy logon route

IV. Related Vulnerabilities

Same product: openEQUELLA
Same vendor: Apereo Foundation
Same weakness: CWE-434