What is CVE-2026-50053?

CVE-2026-50053 is a high-severity vulnerability in Zimbra Collaboration Suite, classified under CWE-642. CVSS score: 8.7/10. Published 2026-10-23.

How severe is CVE-2026-50053?

High severity. CVSS v3 base score is 8.7 out of 10.

Vulnerability in Zimbra Collaboration Suite

CVE-2026-50053

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.

Published 2026-10-23 · last modified 2026-10-23.

CVSS v3 metric

CVSS v3 base score 8.7 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Affected products

Zimbra Collaboration Suite

Weakness classification (CWE)

CWE-642

References

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

Frequently asked questions

What is CVE-2026-50053?: CVE-2026-50053 is a high-severity vulnerability in Zimbra Collaboration Suite, classified under CWE-642. CVSS score: 8.7/10. Published 2026-10-23.
How severe is CVE-2026-50053?: High severity. CVSS v3 base score is 8.7 out of 10.