BleepingComputer reports that updates have been issued by Juniper Networks to resolve a medium-severity Junos OS vulnerability impacting several of its routers, tracked as CVE-2025-21590, which was disclosed by Google's Mandiant team to have been exploited by Chinese cyberespionage hacking group UNC3886 to facilitate the deployment of six different TINYSHELL-based backdoors in an attack campaign last year.
"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. While the complete list of resolved platforms is under investigation, it is strongly recommended to mitigate the risk of exploitation by restricting shell access to trusted users only," said Juniper, which noted the security issue to stem from inadequate isolation or compartmentalization.
Such a flaw has also been added to the Cybersecurity and Infrastructure Security Agency's Known Exploited Vulnerabilities catalog, with federal agencies urged to remediate the bug by Apr. 3.
