CVE-2026-93634: zimbra — Exploit & Fix

Description

A cross-account authorization vulnerability in Zimbra Collaboration Suite (ZCS) allows an authenticated user to insert forged shared-file records into another user's mailbox through FileSharedWithMeRequest. The request bypasses delegated-account authorization and accepts attacker-selected file metadata, owner identifiers and declared sizes without validating a corresponding document share. An attacker can plant entries attributed to another real local account without that account sharing a document. No victim interaction is required. ZCS 10.1.16 and 10.1.20 are affected.

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CVSS v3.1 Score

4.3

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

EPSS — Exploit Prediction

0.0027

Probability of exploitation

0.20%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-639 CWE-639

Affected Products

Vendor	Product	Versions
synacor	zimbra_collaboration_suite	< 10.1.20

References

Advisories & Patches

https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories

Exploits

https://www.rapid7.com/blog/post/ve-breaking-zimbra-identity-boundaries-part-1/

Frequently Asked Questions

What is CVE-2026-93634? +

A cross-account authorization vulnerability in Zimbra Collaboration Suite (ZCS) allows an authenticated user to insert forged shared-file records into another user's mailbox through FileSharedWithMeRequest. The request bypasses delegated-account authorization and accepts attacker-selected file metadata, owner identifiers and declared sizes without validating a corresponding document share. An attacker can plant entries attributed to another real local account without that account sharing a document. No victim interaction is required. ZCS 10.1.16 and 10.1.20 are affected. It has a CVSS v3.1 base score of 4.3 (MEDIUM).

How severe is CVE-2026-93634? +

CVE-2026-93634 has a CVSS v3.1 score of 4.3 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0027, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-93634? +

CVE-2026-93634 affects products from synacor, specifically: zimbra_collaboration_suite. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-93634? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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