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FBI: Patches for Recent Barracuda ESG Zero-Day Ineffective

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Summary

The FBI recently warned that the patches released by Barracuda for a recent Email Security Gateway (ESG) vulnerability (CVE-2023-2868) were ineffective and strongly advised organizations to remove and replace all ESG appliances immediately. The vulnerability has been exploited as a zero-day since October 2022 and is being targeted by a Chinese state-sponsored cyberespionage group (UNC4841). It can be exploited by sending emails containing crafted TAR file attachments that trigger a command injection in the context of the appliance. The FBI advises organizations to scan all networks for connections to indicators of compromise, review email logs, rotate credentials, revoke and reissue associated certificates, review network logs, and monitor the entire network for abnormal activity. Mandiant CEO Kevin Mandia also commented that UNC4841 has been deploying new and novel malware to a small subset of high priority targets since the initial report on the activity.

Q&As

What vulnerability was recently exploited by the Chinese state-sponsored cyberespionage group UNC4841?
The vulnerability recently exploited by the Chinese state-sponsored cyberespionage group UNC4841 is tracked as CVE-2023-2868.

What advice is the FBI giving organizations regarding the vulnerability?
The FBI is advising organizations to “remove all ESG appliances immediately” and to scan for outgoing connections, review email logs, rotate credentials, revoke and reissue associated certificates, review network logs, and monitor the entire network for abnormal activity.

What has the threat actor been deploying since the initial reporting of this vulnerability?
Since the initial reporting of this vulnerability, the threat actor has been deploying new and novel malware to a small subset of high priority targets.

How can organizations identify potential intrusions?
Organizations can identify potential intrusions by scanning the appliance itself for indicators of compromise (IoCs), scanning for outgoing connections, reviewing email logs, rotating credentials, revoking and reissuing associated certificates, reviewing network logs, and monitoring the entire network for abnormal activity.

What has been the shift in tradecraft from China-nexus threat actors?
The shift in tradecraft from China-nexus threat actors has been towards becoming more selective in their follow-on espionage operations.

AI Comments

👍 This article provides a comprehensive overview of the issue and a detailed explanation of the solution.

👎 The article lacks concrete steps that organizations can take to protect themselves from this vulnerability.

AI Discussion

Me: It discusses how the FBI has released a statement saying that the patches released by Barracuda for an exploited ESG zero-day vulnerability (CVE-2023-2868) were not effective. They are now advising organizations to “remove all ESG appliances immediately”.

Friend: Wow, that's concerning! What are the implications of this?

Me: Well, first off, organizations are advised to immediately isolate and replace all affected ESG appliances to avoid any further compromise. Additionally, organizations should scan their networks for connections to the provided list of indicators of compromise, review email logs, rotate credentials, revoke and reissue associated certificates, review network logs, and monitor the entire network for abnormal activity. This is important because the vulnerability impacts the email scanning functionality of Barracuda ESG, so adversaries can exploit it by sending emails containing crafted TAR file attachments that would trigger a command injection in the context of the appliance. The threat actors have been seen leveraging the compromised ESG for lateral movement into the victim’s network, or to send malicious emails to other appliances. So, organizations need to be extra vigilant in order to protect themselves.

Action items

Immediately isolate and replace all affected Barracuda ESG appliances.
Scan the network for connections to the provided list of indicators of compromise.
Rotate credentials, revoke and reissue associated certificates, review network logs, and monitor the entire network for abnormal activity.

Technical terms

CVE-2023-2868: Common Vulnerabilities and Exposures (CVE) is a list of publicly known cybersecurity vulnerabilities and exposures. CVE-2023-2868 is a specific vulnerability that was exploited as a zero-day since at least October 2022.
Zero-Day: A zero-day vulnerability is a computer-software vulnerability that is unknown to those who should be interested in mitigating the vulnerability (including the vendor of the target software).
Indicators of Compromise (IoCs): Indicators of compromise (IoCs) are artifacts observed on a network or in an operating system that, when found, indicate a possible breach or malicious activity.
Malware: Malware is a type of malicious software designed to gain access to or damage a computer system without the owner's informed consent.
Lateral Movement: Lateral movement is the process of moving laterally within a network to gain access to resources and data. It is a common tactic used by attackers to gain access to sensitive information.
Exfiltration: Exfiltration is the process of extracting data from a computer system or network. It is often used by attackers to steal sensitive information.