The FBI has warned that a sophisticated group of attackers have exploited a zero-day flaw in a brand of virtual private networking (VPN) software since May.
The FBI said its forensic analysis showed that the exploitation of the zero-day vulnerability in the FatPipe WARP, MPVPN, and IPVPN software, by an advanced persistent threat (APT) group, went back to at least May 2021. It did not provide any further information about the identity of the group.
The vulnerability allowed the attackers to gain access to an unrestricted file upload function to drop a webshell for exploitation activity with root access, leading to elevated privileges and potential follow-on activity, the FBI said, noting: "Exploitation of this vulnerability then served as a jumping-off point into other infrastructure for the APT actors."
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The FBI said the vulnerability affects all FatPipe WARP, MPVPN, and IPVPN device software prior to the latest version releases, 10.1.2r60p93 and 10.2.2r44p1.
It warned that detection of exploitation activity might be difficult, as cleanup scripts designed to remove traces of the attackers' activity were discovered in most cases.
"Organizations that identify any activity related to these indicators of compromise within their networks should take action immediately," the FBI said in an alert.
"FBI strongly urges system administrators to upgrade their devices immediately and to follow other FatPipe security recommendations such as disabling UI and SSH access from the WAN interface (externally facing) when not actively using it."
FatPipe has its own advisory FPSA006, which notes: "A vulnerability in the web management interface of FatPipe software could allow a remote attacker to upload a file to any location on the filesystem on an affected device.
"The vulnerability is due to a lack of input and validation checking mechanisms for certain HTTP requests on an affected device. An attacker could exploit this vulnerability by sending a modified HTTP request to the affected device."