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A critical vulnerability patched 10 days ago in widely used email software from IT security company Barracuda Networks has been under active exploitation since October. The vulnerability has been used to install multiple pieces of malware inside large organization networks and steal data, Barracuda said Tuesday.

The software bug, tracked as CVE-2023-2868, is a remote command injection vulnerability that stems from incomplete input validation of user-supplied .tar files, which are used to pack or archive multiple files. When file names are formatted in a particular way, an attacker can execute system commands through the QX operator, a function in the Perl programming language that handles quotation marks. The vulnerability is present in the Barracuda Email Security Gateway versions 5.1.3.001 through 9.2.0.006; Barracuda issued a patch 10 days ago.

On Tuesday, Barracuda notified customers that CVE-2023-2868 has been under active exploitation since October in attacks that allowed threat actors to install multiple pieces of malware for use in exfiltrating sensitive data out of infected networks.