Zimbra vulnerabilities & exploitation

Exploitation timeline

Threadlinqs has recorded 5 Zimbra CVEs published between 2024-08-15 and 2026-10-15. The busiest month was 2026-10 (3 new CVEs). 2 of them (40%) are listed in CISA KEV, which means exploitation in the wild has been confirmed.

Most exploited vulnerabilities

Ranked with CISA KEV listings first, then EPSS exploit probability, then CVSS score. Showing 5 of 5 tracked Zimbra CVEs.

• CVE-2026-73570high 8.9KEVEPSS 71.7%2026-08-13
• CVE-2024-27443medium 6.1KEVEPSS 23.6%2024-08-12
• CVE-2026-50055medium 6.5EPSS 0.3%2026-10-08
• CVE-2026-10631medium 6.5EPSS 0.2%2026-10-08
• CVE-2026-50054high 7.1EPSS 0.2%2026-10-08

Products affected

Threadlinqs normalises CPE and CNA product records across all 5 CVEs; 2 distinct Zimbra products are affected. The most frequently affected:

• Collaboration Suite 3 CVEs
• Collaboration 2 CVEs

Threat activity

9 tracked threat campaigns reference Zimbra products or exploit Zimbra CVEs:

• Hackers Target Zimbra Servers in Active Exploitation Campaign via CVE-2026-73570 SNMP Command InjectionCRITICAL2026-08-20
• Operation RoundPress: TA458 Deploys SpyPress Malware via Half-Click Webmail Zero-Days (CVE-2025-27915, CVE-2025-3929, CVE-2026-8496)CRITICAL2026-07-23
• Zimbra Collaboration Suite 10.1.20 Patches Critical Unauthenticated SNMP/Swatchdog Command Injection Plus Six Additional CVEsCRITICAL2026-07-21
• Zimbra Collaboration Suite Classic Web Client Stored XSS (patched in 10.1.19, no CVE yet)CRITICAL2026-07-11
• StrikeShark Campaign: SharkLoader Dropper Targets Governments and Software Developers via N-Day Exploits and Trojanized Installers to Deploy Cobalt StrikeHIGH2026-07-11
• Zimbra Collaboration Suite Critical Stored XSS in Classic Web Client (Patched in ZCS 10.1.19)CRITICAL2026-07-10
• SharkLoader Malware Campaign Uses Fake Cisco AnyConnect and Google Update Installers to Deploy Cobalt StrikeHIGH2026-07-03
• Zimbra Collaboration Suite Stored XSS via CSS @import Active Exploitation (CVE-2025-66376) — Operation GhostMailCRITICAL2026-03-21
• APT28/UAC-0001 Sustained Cyber Espionage Against Ukraine & EU (2024-2026 New TTPs)HIGH2026-02-12

Threat actors targeting Zimbra

Named threat actors attributed to campaigns that involve Zimbra products or CVEs, with the number of linked campaigns:

• APT28 2
• StrikeShark 2

How to prioritise Zimbra patching

This order follows the data Threadlinqs holds for Zimbra, not a generic severity checklist:

• 2 of 5 Zimbra CVEs (40%) are in CISA KEV: treat them as actively exploited and remediate them first, starting with CVE-2026-73570, CVE-2024-27443.
• Outside KEV, the highest EPSS scores are CVE-2026-50055 (0.3%), CVE-2026-10631 (0.2%), CVE-2026-50054 (0.2%).
• 0 CVEs score Critical and 2 High on CVSS v3 (maximum 8.9, average 7); sequence these after KEV and high-EPSS items.
• 3 CVEs have a public exploit or proof of concept recorded, which shortens the time from disclosure to attack.

About this data

Vendor attribution comes from the CNA and CPE product records of each CVE, folded to one vendor name; CVSS, EPSS and KEV status are read from the Threadlinqs CVE catalog; campaign and actor links come from tracked threat records. Counts reflect the data as of 2026-10-12 and refresh daily.