# CVE-2026-93631: Zimbra Collaboration Suite OAuth CSRF in external account linking

Source: https://junglewise.ai/threats/cve-2026-93631-a-cross-site-request-forgery-vulnerability-in-the-oauth-extension  
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-2026-93631 · Severity: high · CVSS 7.1 · Published 2026-10-23

Zimbra Collaboration Suite is an enterprise email and calendar platform. A vulnerability in its OAuth integration allows an attacker to trick a signed-in user into linking the attacker's external account to the victim's mailbox, giving the attacker persistent access to contacts, events, and calendar data. The attacker can read sensitive information and, with bidirectional synchronization enabled, intercept calendar appointments.

Vendors: [Zimbra](https://junglewise.ai/threats/vendors/zimbra).

## Quick answers

**Is CVE-2026-93631 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-93631 being exploited in the wild.

**How severe is CVE-2026-93631?** High severity, with a CVSS score of 7.1, published 23 October 2026.

**Which products and versions are affected?** Zimbra Collaboration Suite Network Edition 10.1.16, 10.1.20.

**Is there a fix for CVE-2026-93631?** 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-2026-93631 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-93631?** Check whether you run Zimbra Collaboration Suite Network Edition 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

The OAuth callback handler in ZCS Network Edition does not bind the authorization state to the initiating session; instead it selects the destination mailbox from the current authentication cookie. An attacker crafts a callback URL with a code for their own provider account and induces a victim to load it while authenticated. This creates a persistent linked external account under the victim's mailbox, allowing data import and calendar interception via CalDAV sync.

## Affected products

- Zimbra Collaboration Suite Network Edition 10.1.16, 10.1.20

## 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/)