Vulnerability · Published Oct 23, 2026 · Assigned by rapid7

CVE-2026-50053Zimbra Collaboration Suite RestFilter Request Attribute Override via Unauthenticated URL Parameters

High 8.7

In plain English

A high-severity security flaw in Zimbra Collaboration Suite from Zimbra. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 22% of all known vulnerabilities).

Severity (CVSS 3.1)8.7High

Exploit odds (30 days)0.3%top 78.4% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

Vendor	Product	Versions
Zimbra	Zimbra Collaboration Suite	0 – through 10.1.17

Weakness: CWE-642 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N

References

https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories vendor-advisory
https://www.rapid7.com/blog/post/ve-breaking-zimbra-identity-boundaries-part-1/ related