Unpatched Fastjson Vulnerability Exploited in Attacks

A critical remote code execution vulnerability in Alibaba's Fastjson library, tracked as CVE-2026-16723, is being actively exploited by threat actors. The flaw affects all versions of Fastjson 1.x from 1.2.68 through 1.2.83, which are now unsupported. Attackers can exploit this issue without authentication or user interaction, allowing them to run arbitrary code on vulnerable servers. Security firms like Imperva have detected attacks targeting multiple industries globally, including finance, healthcare, and retail. Organizations are urged to upgrade to Fastjson 2.x or apply mitigations such as enabling SafeMode.