Russian hackers exploit unpatched Zimbra servers to steal emails
Incidents: Russian hackers exploit Zimbra XSS flaw to steal emails via view-based attacks, targeting unpatched servers globally.
Deep Analysis and Expert Commentary
Laundry Bear's campaign leverages CVE-2025-66376, an XSS flaw in Zimbra's webmail platform, to execute malicious JavaScript when victims view crafted emails. This bypasses traditional phishing, requiring no user interaction. The group targets a broad range of sectors, including defense, government, and energy, exfiltrating emails, credentials, and 2FA tokens. Data is funneled through Flowerbed, a Docker-based infrastructure using cloud servers and VPNs to obscure traffic. Mitigations include immediate patching, reviewing IOCs, and monitoring for anomalous authentication activity, particularly unauthorized 'ZimbraWeb' passcodes. The use of AI in Flowerbed's codebase suggests evolving sophistication in attacker tooling.
Action Items
- Patch Zimbra Collaboration Suite to the latest version immediately.
- Review authentication logs for anomalies and revoke unauthorized 'ZimbraWeb' passcodes.
- Monitor network traffic for connections to known Flowerbed infrastructure domains and IPs.
Original Article Brief Intro
Help Net Security · 2026-07-24 · Incidents: Russian hackers exploit Zimbra XSS flaw to steal emails via view-based attacks, targeting unpatched servers globally.
Related Terms and Notes
CVE IDs
- CVE-2025-66376 — An XSS vulnerability in Zimbra Collaboration Suite allowing malicious JavaScript execution via crafted emails.
Malware Families
- Flowerbed — A Docker-based backend infrastructure used by Laundry Bear for data exfiltration, leveraging cloud servers and VPNs.
- Zimbra Collaboration Suite
Techniques / TTPs
- XSS
Context Notes
- APT
- Cross-Site Scripting
- Email Theft
- Espionage
- Laundry Bear
- Zimbra