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CRITICAL · CVSS 9.8 CISA Known Exploited Vulnerability

CVE-2015-7755

Juniper ScreenOS Improper Authentication Vulnerability

Juniper ScreenOS

Juniper ScreenOS 6.2.0r15 through 6.2.0r18, 6.3.0r12 before 6.3.0r12b, 6.3.0r13 before 6.3.0r13b, 6.3.0r14 before 6.3.0r14b, 6.3.0r15 before 6.3.0r15b, 6.3.0r16 before 6.3.0r16b, 6.3.0r17 before 6.3.0r17b, 6.3.0r18 before 6.3.0r18b, 6.3.0r19 before 6.3.0r19b, and 6.3.0r20 before 6.3.0r21 allows remote attackers to obtain administrative access by entering an unspecified password during a (1) SSH or (2) TELNET session.

CVSS
9.8
CRITICAL
EPSS
61.1%
30-day exploitation
Ransomware groups
0
recorded exploiting
Published
19 Dec 2015
CWE-287

Exploitation status

CISA Known Exploited Vulnerabilities

Listed by CISA on 2 October 2025. US federal agencies were required to remediate it by 23 October 2025.

EPSS — exploitation probability

FIRST puts the probability of exploitation activity in the next 30 days at 61.1%, which is higher than 99.2% of all scored vulnerabilities. EPSS is a forecast of activity, not a measure of severity, and it is rescored daily.

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Frequently asked questions

Is CVE-2015-7755 being exploited by ransomware groups?

No ransomware group in this database is currently recorded as exploiting CVE-2015-7755.

What does CVE-2015-7755 affect?

CVE-2015-7755 affects Juniper ScreenOS. Juniper ScreenOS 6.2.0r15 through 6.2.0r18, 6.3.0r12 before 6.3.0r12b, 6.3.0r13 before 6.3.0r13b, 6.3.0r14 before 6.3.0r14b, 6.3.0r15 before 6.3.0r15b, 6.3.0r16 before 6.3.0r16b, 6.3.0r17 before 6.3.0r17b, 6.3.0r18 before 6.3.0r18b, 6.3.0r19 before 6.3.0r19b, and 6.3.0r20 before 6.3.0r21 allows remote attackers to obtain administrative access by entering an unspecified password during a (1) SSH or (2) TELNET session.

How severe is CVE-2015-7755?

CVE-2015-7755 is rated CRITICAL with a CVSS base score of 9.8. EPSS puts the probability of exploitation in the next 30 days at 61.1%, higher than 99.2% of all scored vulnerabilities. It is listed in the CISA Known Exploited Vulnerabilities catalog, with a federal remediation deadline of 23 October 2025.

How should organisations respond to CVE-2015-7755?

Apply the vendor patch for Juniper ScreenOS as the first priority, and treat any internet-facing instance as the most urgent. Because this vulnerability is associated with ransomware activity, also review whether the affected systems were reachable before patching, rather than assuming that patching alone closes the incident.