CVE-2026-93638 Zimbra Collaboration Suite Pre-Authentication Reflected Cross-Site Scripting via Login Page zrememberme Parameter

Medium 6.1 Published 23 Oct 2026 Updated 28 Oct 2026

Exploited in the wild: Not known
Fix: None listed

What is CVE-2026-93638?

CVE-2026-93638 is a medium-severity vulnerability in Synacor Zimbra Collaboration Suite, published on 23 Oct 2026.

Official description

A reflected cross-site scripting vulnerability in the login page of Zimbra Collaboration Suite (ZCS) allows an unauthenticated attacker to execute JavaScript through the zrememberme parameter. A crafted relogin URL selects a two-factor error display that inserts the parameter into a hidden input attribute without HTML encoding. A victim who opens the URL receives attacker-controlled script and page content under the legitimate Zimbra origin, allowing credential capture through a replacement login form. The relogin path logs out an existing session before rendering the payload, so the demonstrated attack does not inherit that session's mailbox access. ZCS 10.1.16 and 10.1.17 are affected.

Weakness: CWE-79

Which versions are affected by CVE-2026-93638?

It affects 1 product.

Products include Synacor Zimbra Collaboration Suite.

How do I fix CVE-2026-93638?

No fix has been published for CVE-2026-93638 yet. Limit exposure of the affected software until one is available.

Is CVE-2026-93638 being exploited?

There is no known exploitation of CVE-2026-93638 in the wild and no public exploit code.

All Synacor Zimbra Collaboration Suite vulnerabilities

Sources

Also known as GHSA-7vwh-h4vg-w75f.