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A critical security flaw, tracked as CVE-2025-21590, has been identified in Juniper Networks' Junos OS and is currently being exploited in the wild. This vulnerability, characterized by an Improper Isolation or Compartmentalization issue in the kernel, could allow a local attacker with shell access to execute arbitrary code and compromise affected devices. Juniper has released an urgent fix to address this actively exploited flaw, urging users to upgrade to a patched release as soon as possible.

Juniper's Security Incident Response Team (SIRT) has received reports of malicious exploitation of this vulnerability. The Cybersecurity and Infrastructure Security Agency (CISA) has added the flaw to its Known Exploited Vulnerabilities catalog, advising immediate patching. The vulnerability impacts a wide range of Junos OS versions, specifically all versions before 21.2R3-S9, 21.4 versions before 21.4R3-S10, and 22.2 versions before 22.2R3-S6, among others, Juniper Networks strongly advises customers to upgrade to a fixed release as soon as it becomes available.

ImgSrc: static.wixstati

References :

• securityonline.info: Juniper Issues Urgent Fix for Actively Exploited Junos OS Flaw
• Rescana: Rescana Cybersecurity Report: Exploitation in the Wild of CVE-2025-21590

Classification:

• HashTags: #Vulnerability #JuniperNetworks #Cybersecurity
• Company: Juniper Networks
• Target: Junos OS Routers
• Product: Junos OS
• Feature: Kernel Vulnerability
• Malware: CVE-2025-21590
• Type: Vulnerability
• Severity: Critical