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CVE-2025-21590 is an improper isolation vulnerability in the Juniper Networks Junos OS kernel that allows a local attacker with high privileges and shell access to inject arbitrary code into the memory of legitimate processes, bypassing Junos OS Veriexec protections intended to restrict execution to authorized code. The issue affects multiple Junos OS release trains prior to vendor-fixed versions. Exploitation is performed from the underlying shell environment rather than through the Junos CLI alone. Successful exploitation can undermine kernel-enforced compartmentalization and permit execution of unauthorized code within trusted process context, leading to compromise of device integrity and potentially full system control.
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What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
What an attacker gets, and what they’ve been doing with it.
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Patch, then assume compromise.
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
14 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
An improper isolation flaw affecting Juniper MX routers that was exploited by UNC3886 in a notable 2025 zero-day campaign.
An arbitrary code execution vulnerability in Juniper MX Series routers.
A previously noted Juniper Junos OS vulnerability referenced only as part of vendor security history; no technical details are provided in the content.
A locally exploitable Junos OS vulnerability involving improper file origin validation and insufficient process isolation that allows an authenticated attacker with shell access to bypass Veriexec, inject code into legitimate processes, execute malicious code, and fully compromise the device.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.