Fastjson

Weekly Roundup: Critical Vulnerabilities Hit VMware ESX, FortiOS, Chrome, fastjson, Cisco FMC and Ruby on Rails

Security NEXT published its list of the ten most-read articles for the week of July 26 to August 1, 2026. The ranking is dominated by high-severity vulnerabilities affecting widely deployed enterprise platforms. VMware released fixes for serious flaws in ESX and vCenter, while Fortinet confirmed active exploitation of vulnerabilities in FortiOS and VeloCloud Orchestrator. Google patched 370 security issues in Chrome, and a data-conversion library fastjson was found vulnerable with observed attacks. Apple shipped iOS 26.6 and iPadOS 26.6 containing fixes for 87 vulnerabilities, and Cisco warned that its Firewall Management Center is already being exploited. Additional patches addressed OpenAM, Node.js, and a critical flaw dubbed KindaRails2Shell in Ruby on Rails. The list also includes a breach at an ANA Group e-commerce site that may have exposed customer data.

Critical Fastjson Zero-Day CVE-2026-16723 Actively Exploited for Remote Code Execution on Java Servers

A critical zero-day vulnerability tracked as CVE-2026-16723 is being actively exploited in Fastjson 1.x versions ranging from 1.2.68 to 1.2.83. The flaw enables unauthenticated remote code execution on Java servers that process attacker-controlled JSON, particularly when applications run as Spring Boot executable fat JARs. Exploitation succeeds even when AutoType is disabled and does not require elevated privileges or user interaction. No official patch is available for the 1.x branch, forcing organizations to rely on SafeMode activation or migration to fastjson2. Active campaigns have primarily targeted organizations in the United States, with additional activity observed in Singapore and Canada across finance, healthcare, and retail sectors. The vulnerability stems from type resolution logic that allows attackers to bypass restrictions via resource lookups before security controls are applied.