CVE-2026-50053
Published:October 23, 2026
Updated:November 12, 2026
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.
Related Resources (4)
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Contact UsCVSS v4
Base Score:
9.3
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
LOW
User Interaction
PASSIVE
Vulnerable System Confidentiality
HIGH
Vulnerable System Integrity
HIGH
Vulnerable System Availability
NONE
Subsequent System Confidentiality
HIGH
Subsequent System Integrity
HIGH
Subsequent System Availability
NONE
CVSS v3
Base Score:
8.7
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
NONE
Weakness Type (CWE)
External Control of Critical State Data
EPSS
Base Score:
0.29