Vulnerability Description
A request attribute override vulnerability in Zimbra Collaboration Suite (ZCS) allows unauthenticated requests to /h/* to populate servlet attributes intended for trusted internal dispatch. RestFilter copies URL parameters specifying an authentication token, target account, target item and dispatch state into the request attributes consumed by the Classic Web Client. Combined with CVE-2026-10632 on ZCS 10.1.16, this allows an attacker to supply their own valid token and document identifiers and execute JavaScript in another user's signed-in browser session. ZCS 10.1.17 blocks that XSS chain by changing the document renderer, but retains the request attribute override.
CVSS Score
HIGH
Related Weaknesses (CWE)
References
- https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories
- https://www.rapid7.com/blog/post/ve-breaking-zimbra-identity-boundaries-part-1/
FAQ
What is CVE-2026-50053?
CVE-2026-50053 is a vulnerability with a CVSS score of 8.7 (HIGH). A request attribute override vulnerability in Zimbra Collaboration Suite (ZCS) allows unauthenticated requests to /h/* to populate servlet attributes intended for trusted internal dispatch. RestFilter...
How severe is CVE-2026-50053?
CVE-2026-50053 has been rated HIGH with a CVSS base score of 8.7/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-50053?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.