Hackers Exploit Barracuda Zero-Day Flaw Since 2022 to Install Malware

Barracuda Networks, which is currently owned by KKR (Kohlberg Kravis Roberts & Co.,) announced that they had faced a cyber attack in which a Zero Day flaw was exploited, and threat actors extracted data.

The earliest identification of this attack dates back to October 2022.

The flaw existed on their Email Security Gateway (ESG) appliance. The company worked closely with Mandiant cyber security experts to investigate this issue.

The vulnerability was identified to be CVE-2023-2868, and a patch was applied to all ESG appliances worldwide.

CVE-2023-2868: Remote Command Injection Vulnerability

This vulnerability exists due to improper processing, validation, and sanitization of the names of the files within the user-supplied .tar file.

An attacker could exploit this by sending a specially crafted file name in a specified manner, resulting in remote command execution on the system through Perl’s qx operator inside the Email Security Gateway (ESG) product.

Affected Products

Products	Versions
Email Security Gateway Application	5.1.3.001-9.2.0.006

Malware Deployment Using Zero-Day

There were three malware deployed by the threat actors using the Barracuda Email Security Gateway Appliance.

SALTWATER – Trojanised malware for uploading or downloading arbitrary files, command execution, proxy, and tunneling.  It uses five channels for these functionalities: UploadChannel, DownloadChannel, ProxyChannel, TunnelArgs, and ShellChannel.

SEASPY – Persistent backdoor which looks like a legitimate Barracuda Networks Service by establishing itself as a PCAP filter. It monitors port 25 (SMTP) traffic and contains the backdoor functionality.

Mandiant analysis stated that the code could overlap between SEASPY and cd00r, a publicly available backdoor.

SEASIDE – Lua-based module which monitors SMTP HELO/EHLO commands that are used for receiving command and control (C2) IP address and port. It creates a reverse shell by sending the information as arguments to an external library.

File Metadata of the Malware

Module	Name	SHA256
SALTWATER	mod_up.so	1c6cad0ed66cf8fd438974e1eac0bc6dd9119f84892930cb71cb56a5e985f0a4
SEASPY	BarracudaMailService	3f26a13f023ad0dcd7f2aa4e7771bba74910ee227b4b36ff72edc5f07336f115
SEASIDE	mod_require_helo.lua	fa8996766ae347ddcbbd1818fe3a878272653601a347d76ea3d5dfc227cd0bc8

Module	MD5	File Type	Size (Bytes)
SALTWATER	827d507aa3bde0ef903ca5dec60cdec8	ELF x86	1,879,643
SEASPY	4ca4f582418b2cc0626700511a6315c0	ELF x64	2,924,217
SEASIDE	cd2813f0260d63ad5adf0446253c2172	Lua module	2,724

Barracuda has also provided Indicators of Compromise, Network IOCs and YARA rules for detecting this malware.

Barracuda Networks said, “We took immediate steps to investigate this vulnerability.

Our investigation revealed that the vulnerability resulted in unauthorized access to several email gateway appliances. As part of our containment strategy, all ESG appliances received a second patch on May 21, 2023.”

The company also confirmed that no other Barracuda products were affected due to this vulnerability, including the SaaS email security services.

They released patches for fixing this vulnerability as part of their BNSF-36456 on May 20, 2023.

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