Zimbra Collaboration Vulnerability Actively Exploited, CERT Polska Confirms

Poland's national CERT (CERT Polska) has observed active exploitation of CVE-2026-73570, a vulnerability affecting Zimbra Collaboration, the open-source email and groupware platform used by many organizations as a Microsoft Exchange alternative.

Why Email/Groupware Vulnerabilities Carry Outsized Risk

Email and collaboration platforms sit at a uniquely privileged position in most organizations' infrastructure — compromise there can expose not just email content but calendar data, contact information, and often serves as a pivot point for further lateral movement, since email is frequently the trust anchor for password reset and account recovery flows across other systems.

• Organizations running Zimbra Collaboration should prioritize patching this specific CVE immediately, given confirmed active exploitation rather than just theoretical risk
• This lands alongside other actively-exploited vulnerabilities disclosed the same period (NetScaler, Windows Defender, covered separately) — a genuinely active vulnerability disclosure and exploitation period across multiple widely-used platforms simultaneously, worth a broader patch-priority review, not just a single-CVE response