F5 Patches Critical, High-Severity NGINX Vulnerabilities

Summary

F5 has released urgent security updates to address critical and high-severity vulnerabilities in NGINX products. The most severe flaws, CVE-2026-42530 and CVE-2026-42055, could allow unauthenticated attackers to cause a denial-of-service or potentially execute arbitrary code by exploiting use-after-free or heap-based buffer overflow vulnerabilities. Additionally, high-severity bugs in NGINX Gateway Fabric could permit authenticated attackers to inject configuration directives, leading to data exposure or DoS.

Full text

F5 on Wednesday released out-of-band security updates to resolve multiple NGINX vulnerabilities, including critical flaws that could lead to code execution. The most severe are CVE-2026-42530 and CVE-2026-42055 (CVSS score of 9.2), two bugs affecting HTTP modules that could be exploited without authentication to trigger a use-after-free or a heap-based buffer overflow, respectively. Successful exploitation of these issues would result in the NGINX worker process restarting, causing a denial-of-service (DoS) condition. If Address Space Layout Randomization (ASLR) is disabled or can be bypassed, the attacker can execute arbitrary code. F5 has released updated versions of NGINX Plus, NGINX Open Source, and NGINX Gateway Fabric that address these security defects. The company also rolled out fixes for CVE-2026-11311 and CVE-2026-50107, two high-severity vulnerabilities in NGINX Gateway Fabric that could allow authenticated attackers to inject arbitrary NGINX configuration directives. “Successful exploitation may allow the attacker to expose sensitive data from the NGINX pod filesystem, proxy traffic to attacker-controlled endpoints, or cause a denial-of-service (DoS) condition by injecting configuration that prevents NGINX from reloading,” F5 explains.Advertisement. Scroll to continue reading. Additionally, the cybersecurity company announced patches for two medium-severity NGINX flaws that allow remote attackers to disclose memory contents or restart the NGINX worker process, or cause a DoS condition. F5 makes no mention of any of these vulnerabilities being exploited in the wild, but it’s important that users install the patches as NGINX has recently been targeted in attacks. Additional information can be found in the company’s security notification. Related: Rockwell Automation Patches Vulnerabilities in ICS Controllers and Software Related: Microsoft Working on Patch for ‘RoguePlanet’ Zero-Day Related: Oracle’s Second Monthly Security Updates Deliver 245 Patches Related: Chrome and Firefox Updated to Patch Critical, High-Severity Vulnerabilities Written By Ionut Arghire Ionut Arghire is an international correspondent for SecurityWeek. Daily Briefing Newsletter Subscribe to the SecurityWeek Email Briefing for the latest cybersecurity threats, trends, and expert insights. 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Indicators of Compromise

• cve — CVE-2026-42530
• cve — CVE-2026-42055
• cve — CVE-2026-11311
• cve — CVE-2026-50107

Entities