Juniper is warning of unauthorized code in ScreenOS, the operating system for its NetScreen firewalls, that could allow attackers to gain administrative access and decrypt VPN connections.

"During a recent internal code review, Juniper discovered unauthorized code in ScreenOS that could allow a knowledgeable attacker to gain administrative access to NetScreen devices and to decrypt VPN connections," Bob Worrall, Juniper Networks Inc. (NYSE: JNPR)'s SVP and CIO, said on the Juniper support forums Thursday.

"At this time, we have not received any reports of these vulnerabilities being exploited; however, we strongly recommend that customers update their systems and apply the patched releases with the highest priority," Worrall said.

The vulnerability affects NetScreen devices using ScreenOS 6.2.0r15 through 6.2.0r18 and 6.3.0r12 through 6.3.0r20.

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Juniper found no evidence SRX or other Junos devices were affected, Worrall said.

Juniper declined to comment on how the code got into ScreenOS.

A 2013 article in Der Spiegel said the NSA was able to break Juniper firewalls, along with "nearly all the security architecture made by the major players in the industry," including Cisco Systems Inc. (Nasdaq: CSCO), Huawei Technologies Co. Ltd. and Dell Technologies (Nasdaq: DELL)

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