Security Experts:

Connect with us

Hi, what are you looking for?

SecurityWeekSecurityWeek

Application Security

Volexity Warns of ‘Active Exploitation’ of Zimbra Zero-Day

Malware hunters at Volexity are raising the alarm for a Chinese threat actor seen exploiting a zero-day flaw in the Zimbra email platform to infect media and government targets in Europe.

Malware hunters at Volexity are raising the alarm for a Chinese threat actor seen exploiting a zero-day flaw in the Zimbra email platform to infect media and government targets in Europe.

The attacks, which start with a series of targeted spear phishing emails, include the use of an exploit for a still-unpatched cross-site scripting (XSS) flaw in the open-source Zimbra email platform, Volexity said in an advisory released late Thursday.  

The attacks, described as ongoing and “active,” are targeting media and government organizations in Europe.

“At the time of writing, this exploit has no available patch, nor has it been assigned a CVE,” the company said. “This is a zero-day vulnerability.”

In a technical analysis, Volexity said the Chinese hackers launched the campaigns in multiple waves across two attack phases: 

The initial phase was aimed at reconnaissance and involved emails designed to simply track if a target received and opened the messages. The second phase came in several waves that contained email messages luring targets to click a malicious attacker-crafted link. For the attack to be successful, the target would have to visit the attacker’s link while logged into the Zimbra webmail client from a web browser. 

Successful exploitation results in the attacker being able to run arbitrary JavaScript in the context of the user’s Zimbra session.  Volexity’s researchers also observed the attacker attempting to load JavaScript to steal user mail data and attachments. 

“While Volexity only observed [the threat actor] attempting email and attachment theft, the vulnerability could easily allow an attacker to perform other actions in the context of the user’s Zimbra webmail session, including the exfiltration of cookies to allow persistent access to a mailbox and the ability to present a prompt to download malware in the context of a trusted website.

[ READ: Prolific Chinese APT Caught Using ‘MoonBounce’ UEFI Firmware Implant ]

Volexity researchers Steven Adair and Thomas Lancaster said the newest versions of Zimbra — 8.8.15 P29 & P30 — remain vulnerable to session cookie theft. 

Based on BinaryEdge data, approximately 33,000 servers are running the Zimbra email server, although the true number is likely to be higher.  Zimbra boasts that about 200,000 businesses, and over 1,000  government and financial institutions use the software.

The company said it was unable to attribute this attack to a previously known threat actor but found artifacts to suggest it is the work of a nation-state backed operator.

“Based on the targeted organization and specific individuals of the targeted organization, and given the stolen data would have no financial value, it is likely the attacks were undertaken by a Chinese APT actor,” Volexity said.

The company released indicators of compromise data to help defenders manage blocking at the gateway and network level and urged Zimbra users to analyze historical referrer data for suspicious access and referrers. 

“Users of Zimbra should consider upgrading to version 9.0.0, as there is currently no secure version of 8.8.15,” the company said.

Related: Vulnerabilities Allow Hacking of Zimbra Webmail Servers With Single Email

Related: Poisoned Installers Found in SolarWinds Hackers Toolkit

Related: Microsoft: Exchange Server Zero-Days Under Attack by Chinese APT Group

Related: Prolific Chinese APT Caught Using ‘MoonBounce’ UEFI Firmware Implant

Written By

Ryan Naraine is Editor-at-Large at SecurityWeek and host of the popular Security Conversations podcast series. He is a security community engagement expert who has built programs at major global brands, including Intel Corp., Bishop Fox and GReAT. Ryan is a founding-director of the Security Tinkerers non-profit, an advisor to early-stage entrepreneurs, and a regular speaker at security conferences around the world.

Click to comment

Daily Briefing Newsletter

Subscribe to the SecurityWeek Email Briefing to stay informed on the latest threats, trends, and technology, along with insightful columns from industry experts.

Join this webinar to learn best practices that organizations can use to improve both their resilience to new threats and their response times to incidents.

Register

Join this live webinar as we explore the potential security threats that can arise when third parties are granted access to a sensitive data or systems.

Register

Expert Insights

Related Content

Application Security

Cycode, a startup that provides solutions for protecting software source code, emerged from stealth mode on Tuesday with $4.6 million in seed funding.

Vulnerabilities

Less than a week after announcing that it would suspended service indefinitely due to a conflict with an (at the time) unnamed security researcher...

Data Protection

The CRYSTALS-Kyber public-key encryption and key encapsulation mechanism recommended by NIST for post-quantum cryptography has been broken using AI combined with side channel attacks.

Data Protection

The cryptopocalypse is the point at which quantum computing becomes powerful enough to use Shor’s algorithm to crack PKI encryption.

Cybercrime

The changing nature of what we still generally call ransomware will continue through 2023, driven by three primary conditions.

Data Breaches

LastPass DevOp engineer's home computer hacked and implanted with keylogging malware as part of a sustained cyberattack that exfiltrated corporate data from the cloud...

Application Security

PayPal is alerting roughly 35,000 individuals that their accounts have been targeted in a credential stuffing campaign.

Cybercrime

No one combatting cybercrime knows everything, but everyone in the battle has some intelligence to contribute to the larger knowledge base.