Juniper revised the list of ScreenOS versions that contain a backdoor allowing attackers to bypass authentication and gain administrative access to NetScreen enterprise firewall devices.
The networking equipment manufacturer announced last week that it found, during an internal audit, two instances where rogue code was added to its ScreenOS operating system without authorization. The code could be used by attackers to gain privileged access to NetScreen firewall devices and to decrypt VPN connections.
The company said at the time that ScreenOS versions 6.2.0r15 through 6.2.0r18 and 6.3.0r12 through 6.3.0r20 were vulnerable, but an analysis by researchers from security firm Rapid7 revealed that not all listed versions are vulnerable to both issues.
"We were unable to identify this [authentication] backdoor in versions 6.2.0r15, 6.2.0r16, 6.2.0r18 and it is probably safe to say that the entire 6.2.0 series was not affected by this issue (although the VPN issue was present)," said HD Moore, chief research officer at Rapid7, in a blog post Sunday.
In the 6.3.0 series, the authentication bypass code, which relies on a hard-coded master password that works for any account, was confirmed in 6.3.0r17 and 6.3.0r19, but not in 6.3.0r12 or 6.3.0r14. Based on the release dates of these versions, the backdoor was added sometime in late 2013, HD Moore said.
Late Sunday, Juniper updated its advisory to clarify that the impact, as far as number of versions is concerned, is more limited than initially thought. The administrative access issue only affects ScreenOS 6.3.0r17 through 6.3.0r20, while the VPN decryption issue affects ScreenOS 6.2.0r15 through 6.2.0r18 and 6.3.0r12 through 6.3.0r20, the company said.
In late December 2013, the German news magazine Der Spiegel published a catalog of software and hardware implants used by the U.S. National Security Agency that was leaked by former NSA contractor Edward Snowden.
The catalog described a technique code-named FEEDTROUGH that could be used to persistently install two software implants -- BANANAGLEE and ZESTYLEAK -- on Juniper NetScreen firewalls.
"FEEDTROUGH operates every time the particular Juniper firewall boots," its description reads. "The first hook takes it to the code which checks to see if the OS is in the database, if it is, then a chain of events ensures the installation of either one or both implants."
FEEDTROUGH is probably not connected to the backdoor found by Juniper now, because the leaked NSA catalog itself predates the addition of the rogue code in late 2013. However, it does indicate that Juniper knew for almost two years from public reports that its devices were targeted by at least one intelligence agency and raises the question of why the company didn't discover the security issues sooner.
This only complicates the questions about who added the rogue code and how it was done, which the security community is hoping Juniper will eventually address.
Juniper NetScreen users should upgrade their devices to the newly released ScreenOS versions 6.2.0r19 or 6.3.0r21, or should install a backdoor-free version of the firmware they're already running, which Juniper also made available. These re-releases have the original version numbers followed by the letter b.
The likelihood of attacks is high, especially since the backdoor password is now public.