Cisco is warning that a high-severity flaw in its network security software is being actively exploited – allowing remote, unauthenticated attackers to access sensitive data.
Patches for the vulnerability (CVE-2020-3452) in question, which ranks 7.5 out of 10 on the CVSS scale, were released last Wednesday. However, attackers have since been targeting vulnerable versions of the software, where the patches have not yet been applied.
“The Cisco Product Security Incident Response Team (PSIRT) is aware of the existence of public exploit code and active exploitation of the vulnerability that is described in this advisory,” according to Cisco.
The flaw specifically exists in the web services interface of Firepower Threat Defense (FTD) software, which is part of Cisco’s suite of network security and traffic management products; and its Adaptive Security Appliance (ASA) software, the operating system for its family of ASA corporate network security devices.
The potential threat surface is vast: Researchers with Rapid7 recently found 85,000 internet-accessible ASA/FTD devices. Worse, 398 of those are spread across 17 percent of the Fortune 500, researchers said.
The flaw stems from a lack of proper input validation of URLs in HTTP requests processed by affected devices. Specifically, the flaw allows attackers to conduct directory traversal attacks, which is an HTTP attack enabling bad actors to access restricted directories and execute commands outside of the web server’s root directory.
Soon after patches were released, proof-of-concept (POC) exploit code was released Wednesday for the flaw by security researcher Ahmed Aboul-Ela.
A potential attacker can view more sensitive files within the web services file system: The web services files may have information such as WebVPN configuration, bookmarks, web cookies, partial web content and HTTP URLs.
There’s a proof of concept doing the rounds for directory path traversal (yes, it’s 1998 again) in Cisco AnyConnect SSL VPN.
It’s already being mass spammed across internet.
As far as I can see people can only read LUA source files so far, so not terribly problematic as is. https://t.co/kSIFQdz1go
— Kevin Beaumont (@GossiTheDog) July 24, 2020
Cisco said the vulnerability affects products if they are running a vulnerable release of Cisco ASA Software or Cisco FTD Software, with a vulnerable AnyConnect or WebVPN configuration: “The web services file system is enabled when the affected device is configured with either WebVPN or AnyConnect features,” according to its advisory. However, “this vulnerability cannot be used to obtain access to ASA or FTD system files or underlying operating system (OS) files.”
Researchers with Rapid7 say that since the patch was issued, only about 10 percent of Cisco ASA/FTD devices detected as internet-facing have been rebooted – which is a “likely indicator they’ve been patched.” Only 27 of the 398 detected in Fortune 500 companies appear to have been rebooted.
Researchers encourage immediate patching of vulnerable ASA/FTD installations “to prevent attackers from obtaining sensitive information from these devices which may be used in targeted attacks.”
“Cisco has provided fixes for all supported versions of ASA and FTD components,” said researchers. “Cisco ASA Software releases 9.5 and earlier, as well as Release 9.7, along with Cisco FTD Release 6.2.2 have reached the end of software maintenance and organizations will have to upgrade to a later, supported version to fix this vulnerability.”
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