CVE-2026-93628

MEDIUM CVSS 5.3
Published: 2026-10-23
Modified: 2026-10-23
Enriched via mock
Tenable Plugin

Checking the public Tenable catalog…

AI Threat Summary

CVE-2026-93628 is a moderate vulnerability with a CVSS score of 5.3 affecting the target software. Authentication can be bypassed allowing unauthenticated access. Threat hunters should monitor for exploit attempts and apply vendor patches immediately.

Description

An attendee authentication vulnerability in the email calendar processing of Zimbra Collaboration Suite (ZCS) allows an unauthenticated sender to forge another attendee's response to an existing meeting. Zimbra passes a null sender identity when processing iCalendar REPLY components, causing the attendee authorization filter to be skipped. An attacker who knows the meeting UID, organizer address and attendee address can send a non-outdated reply that changes the attendee's participation status in the organizer's calendar. The change occurs automatically during delivery without organizer or attendee interaction. ZCS 10.1.16 and 10.1.21 are affected.

Attack Chain
1
Reconnaissance

Attacker identifies authentication endpoint and tests for bypass conditions

2
Initial Access

Attacker exploits CVE-2026-93628 authentication flaw to gain unauthorized access without valid credentials

3
Discovery

Attacker enumerates accessible resources, users, and configurations

4
Collection

Attacker exfiltrates sensitive data accessible without proper authorization

MITRE ATT&CK Techniques
T1078 Valid Accounts
Initial Access

Authentication bypass grants attacker access as legitimate user

T1548 Abuse Elevation Control Mechanism
Privilege Escalation

Bypassed auth may grant elevated or admin-level permissions

Indicators of Compromise
Type Value Description
user_agent Mozilla/5.0 (compatible; exploit/1.0) Generic exploit scanner user agent pattern
url /api/vuln-endpoint?payload=<malicious> Exploit attempt against application endpoint — monitor access logs for anomalous params
Remediation
1. Apply vendor-supplied security patches immediately. 2. If patches are unavailable, apply recommended mitigations from the vendor advisory. 3. Enable WAF rules or IDS signatures to detect exploitation attempts. 4. Monitor logs for indicators of compromise listed above. 5. Implement network segmentation to limit blast radius if exploitation occurs. 6. Subscribe to vendor security advisories for this product.
Quick Facts
CVE ID CVE-2026-93628
CVSS Score 5.3
Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Published 2026-10-23
Exploited No
CISA KEV No
PoC Not public
References
External Resources
NVD Entry BleepingComputer The Hacker News