---
id: "CVE-2026-93638"
kind: "vulnerability"
aliases: ["CVE-2026-93638"]
title: "Zimbra Collaboration: login page reflected XSS steals credentials via crafted URL"
severity: "medium"
cvss: 6.1
epss: 0.00286
exploited: false
status: "open"
category: "infrastructure"
products: []
ecosystems: []
tags: ["email", "infrastructure", "self-hosted", "zimbra"]
not_affected_if: ["other-zcs-versions"]
published_at: "2026-10-23T14:17:57+00:00"
first_seen_at: "2026-10-23T21:57:34+00:00"
updated_at: "2026-10-25T12:38:49+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-93638", "first_seen_at": "2026-10-23T21:57:34+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-93638", "first_seen_at": "2026-10-25T12:38:49+00:00"}]
---

# Zimbra Collaboration: login page reflected XSS steals credentials via crafted URL

A reflected cross-site scripting flaw in the Zimbra Collaboration Suite login page lets an unauthenticated attacker run JavaScript through the zrememberme parameter in a crafted relogin URL. A victim who opens the link can have a fake login form shown under the real Zimbra origin, which captures their credentials.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed version with `zmcontrol -v` on the Zimbra server; versions 10.1.16 and 10.1.17 are affected.
- Review web access logs for requests to the login page carrying a zrememberme parameter with script-like content.

## Fix

- Move ZCS 10.1.16 and 10.1.17 to a fixed release from Zimbra (fixed version unknown from the sources).
- Until patched, unknown.

## Timeline

- 2026-10-23T21:57:34+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-93638
- 2026-10-25T12:38:49+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-93638

## From the sources

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.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_