Risky Bulletin Newsletter
July 24, 2026
Risky Bulletin: Western cyber agencies warn of Russian hacks of Zimbra servers
Presented by
News Editor
Cybersecurity and intelligence agencies from multiple Western countries have issued joint security advisories on Thursday warning of a major Russian hacking campaign that's targeting Zimbra email servers.
The attacks have been going on since last year. The zero-day, tracked as CVE-2025-66376, was patched in November but attacks have been traced back to at least July.
The zero-day itself is a stored cross-site scripting (XSS) bug that allows the attackers to load malicious code inside a Zimbra webmail client via the CSS @import feature. The malicious code would load a web tool called Ulej (Russian for Beehive) that could be used to harvest credentials, session tokens, backup 2FA codes, browser-saved passwords, and the contents of the victim’s mailbox going back 90 days.