Zimbra 10.1.16-17 Request Attribute Override XSS via /h/*
CVE-2026-50053 Published on October 23, 2026
Zimbra Collaboration Suite RestFilter Request Attribute Override via Unauthenticated URL Parameters
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.
Vulnerability Analysis
CVE-2026-50053 can be exploited with network access, requires user interaction and a small amount of user privileges. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have a high impact on confidentiality and integrity, and no impact on availability.
Weakness Type
External Control of Critical State Data
The software stores security-critical state information about its users, or the software itself, in a location that is accessible to unauthorized actors.
Products Associated with CVE-2026-50053
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Affected Versions
Zimbra Collaboration Suite:- Before and including 10.1.17 is affected.