Skip to main content Tech Radar Pro Tech Radar Gaming Tech Radar Pro TechRadar the business technology experts Search TechRadar View Profile België (Nederlands) Deutschland North America US (English) Australasia New Zealand Expert Insights Website builders Web hosting Best web hosting Best website builder Best office chairs Expert Insights Juniper patches security flaws which could have let hackers take over your router Sead Fadilpašić 14 March 2025 Juniper flaw being abused by Chinese hackers has now been patched When you purchase through links on our site, we may earn an affiliate commission. Here’s how it works. (Image credit: Shutterstock) Juniper Networks has patched a vulnerability in its routers The flaw was being abused by Chinese threat actors Multiple devices were vulnerable Juniper Networks has released a patch for a vulnerability that was being exploited in the wild to attack some of its router brands. According to the company’s security advisory, the bug is an improper isolation, or compartmentalization weakness, and it’s tracked as CVE-2025-21590. It was given a severity score of 6.7 (medium). The bug is used by Chinese hackers, who had been exploiting it since 2024 to backdoor vulnerable Juniper routers that reached end-of-life, a recent Madiant security report revealed. You may like Chinese hackers targeting Juniper Networks routers, so patch now Juniper Session Smart routers have a critical flaw, so patch now Chinese hackers "In mid 2024, Mandiant discovered threat actors deployed custom backdoors operating on Juniper Networks' Junos OS routers," the cybersecurity company explained. "Mandiant attributed these backdoors to the China-nexus espionage group, UNC3886. Mandiant uncovered several TINYSHELL based backdoors operating on Juniper Networks' Junos OS routers." UNC3886 was observed in the past targeting defense, technology, and telecommunications organizations with sophisticated malware, deployed through zero-day vulnerabilities. It affects at least these models: NFX-Series, Virtual SRX, SRX-Series Branch, SRX-Series HE, EX-Series, QFX-Series, ACX, and MX-Series, however, Juniper Networks said that it is still investigating the vulnerability and that the full list could be different. The bug can be exploited to allow local attackers with high privileges to run arbitrary code on the routers, and thus compromise them. Are you a pro? Subscribe to our newsletter Sign up to the TechRadar Pro newsletter to get all the top news, opinion, features and guidance your business needs to succeed! Contact me with news and offers from other Future brandsReceive email from us on behalf of our trusted partners or sponsorsBy submitting your information you agree to the Terms & Conditions and Privacy Policy and are aged 16 or over. "At least one instance of malicious exploitation (not at Amazon) has been reported to the Juniper SIRT,” Juniper said in its advisory. “Customers are encouraged to upgrade to a fixed release as soon as it's available and in the meantime take steps to mitigate this vulnerability." The issue was resolved in 21.4R3-S10, 22.2R3-S6, 22.4R3-S6, 23.2R2-S3, 24.2R1-S2, 24.2R2, 24.4R1, and all subsequent releases. At the same time, CISA added the bug to its Known Exploited Vulnerabilities catalog (KEV), confirming reports of in-the-wild abuse, and giving Federal Civilian Executive Branch (FCEB) agencies three weeks to apply the patch, or stop using vulnerable solutions. Via BleepingComputer You might also like Chinese hackers targeting Juniper Networks routers, so patch now We've rounded up the best password managers Take a look at our guide to the best authenticator app Sead Fadilpašić Social Links Navigation Sead is a seasoned freelance journalist based in Sarajevo, Bosnia and Herzegovina. He writes about IT (cloud, IoT, 5G, VPN) and cybersecurity (ransomware, data breaches, laws and regulations). In his career, spanning more than a decade, he’s written for numerous media outlets, including Al Jazeera Balkans. He’s also held several modules on content writing for Represent Communications. You must confirm your public display name before commenting Please logout and then login again, you will then be prompted to enter your display name. 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