Hack Attack: Winter Vivern Turns Your Inbox into a Spectator Sport

Just when you thought it was safe to check your email, Winter Vivern, a team of pro-Russian hackers, exploits a zero-day vulnerability in Roundcube, a popular webmail software, turning email reading into a dangerous spectator sport.

Hot Take:

Just when you thought it was safe to check your email, a team of pro-Russian hackers say ‘Nostrovia!’ and show us that your inbox can be a veritable Pandora’s Box. The cyber bogeymen, known as Winter Vivern, have exploited a zero-day vulnerability in Roundcube, a popular webmail software. This isn’t your average phishing scam; they’ve turned email reading into a spectator sport, with the spectators being the hackers themselves. And all it takes is viewing an email. No clicking, no downloading, just looking. Who knew reading could be so dangerous?

Key Points:

  • Winter Vivern, a pro-Russian and Belarus hacking group, exploited a zero-day vulnerability in Roundcube, a popular webmail software.
  • The vulnerability allowed the hackers to inject JavaScript into the Roundcube server application just by viewing a malicious email.
  • The attacks started on October 11, with ESET detecting them a day later and a patch issued by Roundcube developers on October 14.
  • Winter Vivern has been active since at least 2020, targeting governments and think tanks, primarily in Europe and Central Asia.
  • The email used in the recent campaign came from the address team.management@outlook.com and had the subject “Get started in your Outlook.”

The Back Channel:

A Cold Winter's Hack

Spearheaded by Winter Vivern, this hacking campaign exploits a critical cross-site scripting error in Roundcube, a webmail service used by over a thousand webmail services and millions of end users. And the scary part? The attack is triggered by merely viewing a malicious email, causing the server to send emails from selected targets to a server controlled by the hackers.

Fast and Furious: Cybersecurity Edition

The timeline of the attacks is a testament to the rapid-fire world of cybersecurity. The attacks began on October 11, and ESET detected them a day later. Roundcube developers were alerted on the same day, and a patch was issued just three days later.

Repeat Offenders

This isn't Winter Vivern's first rodeo. The group has been operating since at least 2020, targeting governments and think tanks throughout Europe and Central Asia. In fact, earlier this year, they were spotted targeting US government officials who had voiced support for Ukraine. It seems these cyber troublemakers have a taste for high-stakes targets.

Hide Yo' Emails, Hide Yo' Servers

The final JavaScript payload instructed vulnerable servers to list folders and emails in the target’s email account and to exfiltrate email messages to an attacker-controlled server. This should serve as a stark reminder to anyone using Roundcube: make sure your software is running a patched version, or you might find yourself in the cyber equivalent of a Russian winter – cold, dark, and not at all pleasant.
Tags: , JavaScript injection, Patched software, Pro-Russian hackers, Roundcube vulnerability, Winter Vivern, XSS bug