Juniper ScreenOS Backdoors: Hardcoded SSH/Telnet Password and Dual_EC VPN Decryption
On 17 December 2015 Juniper disclosed "unauthorized code" in ScreenOS: an administrative authentication backdoor (CVE-2015-7755) and a change enabling passive decryption of VPN traffic (CVE-2015-7756).
02Deep-Dive Technical Analysis
CVE-2015-7755 (ScreenOS 6.3.0r17–r20) added a strcmp against the password "<<< %s(un='%s') = %u", disguised as a debug format string, granting admin access over SSH/Telnet. CVE-2015-7756 (6.2.0r15–r18, 6.3.0r12–r20) replaced the Q point of the Dual_EC_DRBG generator Juniper had shipped since 2008; a reseeding bug in the X9.31 PRNG meant to post-process it exposed raw Dual_EC output in IKE, so whoever knew the discrete log of the new Q could recover VPN keys passively (Checkoway et al.).
03Vulnerability & Exploit Flow
Hardcoded master password in the SSH/Telnet authentication path, and a substituted Dual_EC Q constant enabling passive IKE key recovery.
04Recommended Defense & Mitigation Protocol
Patched ScreenOS releases removing the backdoor and Dual_EC, reproducible builds and source-integrity auditing, and avoiding trapdoor-capable RNGs.
05Security Impact & Geopolitical Consequence
A real-world demonstration that a "NOBUS" backdoor can be re-keyed by a third party; the perpetrator is not officially attributed, though Bloomberg reported in 2021, citing sources, that China-linked APT 5 made the 2012 Dual_EC change.
06Authoritative Standards & External References
07Related Topic Cluster Records
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