Friday, 18 December 2015

"Unauthorized code" in Juniper firewalls decrypts encrypted VPN traffic

Juniper Networks published an advisory saying that NetScreen firewalls using ScreenOS 6.2.0r15 through 6.2.0r18 and 6.3.0r12 through 6.3.0r20 contain unauthorized code that surreptitiously decrypts the VPN traffic by giving attackers administrative access. 

This system "backdoor" requires immediate patching! The vulnerability was discovered during a recent internal code review[1]. The "unauthorised code" in ScreenOS could allow a knowledgeable attacker to gain administrative access to NetScreen appliances and to decrypt VPN connections. 

Juniper Networks explained in a separate advisory that there are two separate vulnerabilities which are both described as “Unauthorised Code”.

The first flaw allows unauthorized remote administrative access to an affected device over SSH or telnet. Exploits can lead to complete compromise. "The second issue may allow a knowledgeable attacker who can monitor VPN traffic to decrypt that traffic," the advisory said. "It is independent of the first issue. There is no way to detect that this vulnerability was exploited." [2]

This Github repository contains notes, binaries, and related information from the analysis of the CVE-2015-7755 & CVE-2015-7756 issues within Juniper ScreenOS. See a detailed analysis by Rapid7

You will find it very interesting that the argument to the strcmp call is: <<< %s(un='%s') = %u, which is actually the backdoor password, and was presumably chosen so that it would be mistaken for one of the many other debug format strings in the code. 

It is indeed very suspicious how the unauthorised code ended up there. ScreenOS software releases are available at :



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