# CVE-2026-93638: Zimbra Collaboration Suite reflected cross-site scripting in login

Source: https://junglewise.ai/threats/cve-2026-93638-a-reflected-cross-site-scripting-vulnerability-in-the-login-page  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-23. Updated: 2026-10-23  
License: CC BY 4.0 with a link back

CVE-2026-93638 · Severity: medium · CVSS 6.1 · Published 2026-10-23

Zimbra Collaboration Suite is an enterprise email and collaboration platform used by organizations for email, calendars, and file sharing. An unauthenticated attacker can exploit a reflected XSS vulnerability in the login page to inject malicious JavaScript that captures user credentials through a fake login form. The vulnerability allows attackers to redirect victims to crafted URLs that execute attacker-controlled code under Zimbra's legitimate domain.

Technologies: [Zimbra Collaboration Suite](https://junglewise.ai/threats/technologies/collaboration). Vendors: [Zimbra](https://junglewise.ai/threats/vendors/zimbra).

## Quick answers

**Is CVE-2026-93638 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-93638 being exploited in the wild.

**How severe is CVE-2026-93638?** Medium severity, with a CVSS score of 6.1, published 23 October 2026.

**Which products and versions are affected?** Zimbra Collaboration Suite 10.1.16, 10.1.17.

**Is there a fix for CVE-2026-93638?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-93638 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-93638?** Check whether you run Zimbra Collaboration Suite at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A reflected XSS vulnerability exists in the relogin path due to improper HTML encoding of the zrememberme parameter when displaying a two-factor authentication error. The parameter is inserted into a hidden input attribute without sanitization, allowing JavaScript execution in the victim's browser under the Zimbra origin. An attacker crafts a malicious URL that, when clicked by a user, logs out any existing session and renders the injected payload, enabling credential theft via a replacement login form.

## Affected products

- Zimbra Collaboration Suite 10.1.16, 10.1.17

## Timeline

- 2026-10-23: disclosed

## References

- [https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories](https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories)
- [https://www.rapid7.com/blog/post/ve-breaking-zimbra-identity-boundaries-part-1/](https://www.rapid7.com/blog/post/ve-breaking-zimbra-identity-boundaries-part-1/)

## Related threats

- [Zimbra Collaboration Suite local privilege escalation in dnscache](https://junglewise.ai/threats/cve-2026-93640-a-local-privilege-escalation-vulnerability-in-the-optional)
- [Zimbra Collaboration Suite authorization bypass in Zimlet configuration](https://junglewise.ai/threats/cve-2026-93639-a-missing-authorization-vulnerability-in-zimbra-collaboration)
- [Zimbra Collaboration Suite LDAP filter injection](https://junglewise.ai/threats/cve-2026-93636-an-ldap-filter-injection-vulnerability-in-zimbra-collaboration)
- [Zimbra Collaboration Suite cross-account authorization bypass in FileSharedWithMeRequest](https://junglewise.ai/threats/cve-2026-93634-a-cross-account-authorization-vulnerability-in-zimbra)
- [Zimbra Collaboration Suite CSS sanitization bypass](https://junglewise.ai/threats/cve-2026-93633-a-css-sanitization-vulnerability-in-zimbra-collaboration-suite)