Description
The open-vsx.org deployment returned Access-Control-Allow-Origin reflecting the requesting origin together with Access-Control-Allow-Credentials: true on the authenticated /user/ endpoints. A page on any origin could therefore issue credentialed requests to the service in a logged-in user's browser and read the responses.



This exposed /user (login name, avatar, homepage, tokens URL), /user/tokens, /user/namespaces, /user/extensions, /user/search/{name} and /user/namespace/{name}/members, and — because /user/csrf was readable the same way — allowed the CSRF protection on write endpoints to be defeated. Chaining the two, an attacker page could call /user/token/create and exfiltrate a personal access token carrying publish and delete rights over the victim's namespaces.



The headers were emitted by the CDN/edge layer, not by the application: the Open VSX software sets allowCredentials(true) in exactly one place, against a single exact origin derived from ovsx.webui.url, and defines no CORS mapping on /user/ beyond it. No configuration of the software produces origin reflection with credentials.
Published: 2026-09-22
Score: 8.7 High
EPSS: n/a
KEV: No
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Remediation

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History

Tue, 22 Sep 2026 14:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}


Tue, 22 Sep 2026 09:45:00 +0000

Type Values Removed Values Added
Description The open-vsx.org deployment returned Access-Control-Allow-Origin reflecting the requesting origin together with Access-Control-Allow-Credentials: true on the authenticated /user/ endpoints. A page on any origin could therefore issue credentialed requests to the service in a logged-in user's browser and read the responses. This exposed /user (login name, avatar, homepage, tokens URL), /user/tokens, /user/namespaces, /user/extensions, /user/search/{name} and /user/namespace/{name}/members, and — because /user/csrf was readable the same way — allowed the CSRF protection on write endpoints to be defeated. Chaining the two, an attacker page could call /user/token/create and exfiltrate a personal access token carrying publish and delete rights over the victim's namespaces. The headers were emitted by the CDN/edge layer, not by the application: the Open VSX software sets allowCredentials(true) in exactly one place, against a single exact origin derived from ovsx.webui.url, and defines no CORS mapping on /user/ beyond it. No configuration of the software produces origin reflection with credentials.
Title Reflected arbitrary origins with credentials, allowing cross-origin reads of authenticated user data
Weaknesses CWE-942
References
Metrics cvssV4_0

{'score': 8.7, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N'}


Subscriptions

No data.

cve-icon MITRE

Status: PUBLISHED

Assigner: eclipse

Published:

Updated: 2026-09-22T13:06:14.742Z

Reserved: 2026-09-14T07:44:22.377Z

Link: CVE-2026-90882

cve-icon Vulnrichment

Updated: 2026-09-22T13:06:11.317Z

cve-icon NVD

Status : Received

Published: 2026-09-22T10:17:10.000

Modified: 2026-09-22T14:17:17.697

Link: CVE-2026-90882

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-22T10:30:17Z

Weaknesses
  • CWE-942

    Permissive Cross-domain Security Policy with Untrusted Domains