CVE-2026-93636: zimbra — Exploit & Fix

Description

An LDAP filter injection vulnerability in Zimbra Collaboration Suite (ZCS) allows an authenticated user to query otherwise unreturned attributes of calendar resources through SearchCalendarResourcesRequest. Zimbra escapes search values but inserts the supplied attribute names directly into LDAP filter expressions without validation. An attacker can inject additional conditions and use repeated matching queries to recover readable resource attributes such as internal mailbox hostnames and mail transport routes. The search remains restricted to calendar-resource objects and the LDAP service account's access rights. ZCS 10.1.16 and 10.1.21 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:L/I:N/A:N

EPSS — Exploit Prediction

0.0034

Probability of exploitation

0.28%

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-90 CWE-90

Affected Products

Vendor	Product	Versions
synacor	zimbra_collaboration_suite	< 10.1.21

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-2026-93636? +

An LDAP filter injection vulnerability in Zimbra Collaboration Suite (ZCS) allows an authenticated user to query otherwise unreturned attributes of calendar resources through SearchCalendarResourcesRequest. Zimbra escapes search values but inserts the supplied attribute names directly into LDAP filter expressions without validation. An attacker can inject additional conditions and use repeated matching queries to recover readable resource attributes such as internal mailbox hostnames and mail transport routes. The search remains restricted to calendar-resource objects and the LDAP service account's access rights. ZCS 10.1.16 and 10.1.21 are affected. It has a CVSS v3.1 base score of 4.3 (MEDIUM).

How severe is CVE-2026-93636? +

CVE-2026-93636 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 0.0034, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-93636? +

CVE-2026-93636 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-2026-93636? +

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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