CVE-2015-7755

CVE-2015-7755 is an improper authentication flaw (CWE-287) in Juniper ScreenOS that allows an unauthenticated remote attacker to gain administrative access to affected Juniper firewalls. It is triggered remotely via the device's administrative access path — widely reported as a hardcoded-credential backdoor reachable over SSH/Telnet management sessions, so any network that can reach the management interface is exposed. A successful attacker gains full administrator control of the firewall, enabling configuration changes, traffic manipulation, credential theft, and persistence. Only organizations running Juniper ScreenOS (legacy NetScreen/SSG firewall deployments) are affected. CISA added the flaw to the Known Exploited Vulnerabilities catalog on 2025-10-02, confirming exploitation in the wild; no public proof-of-concept is known.

What to do: Per the CISA required action and BOD 22-01, upgrade ScreenOS to a fixed release per Juniper's advisory, or if fixed versions are unavailable for your hardware, discontinue use or immediately restrict SSH and Telnet administrative access to trusted management networks. Audit device logs for unexpected administrative logins, rotate or reset administrative credentials, and treat any long-lived ScreenOS firewall as potentially compromised given the backdoor history and current KEV listing.