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VulnerabilitiesJun 18, 2026

F5 issues out-of-band patches for critical NGINX vulnerabilities

F5 releases out-of-band patches for two critical NGINX RCE vulnerabilities

F5 released emergency security updates addressing two critical-severity vulnerabilities in NGINX web server modules (CVE-2026-42530 and CVE-2026-42055) that allow unauthenticated remote attackers to execute code or trigger denial-of-service attacks on vulnerable systems. The flaws involve use-after-free and heap-based buffer overflow issues in the NGINX worker process and can lead to code execution when ASLR is disabled or bypassed. F5 also patched two high-severity NGINX Gateway Fabric flaws allowing authenticated configuration injection attacks.

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The lesson from this incident

Full lesson

F5 issued emergency out-of-band patches for two critical vulnerabilities in NGINX — a use-after-free flaw and a heap-based buffer overflow — both of which can be exploited by unauthenticated remote attackers to execute arbitrary code or cause denial-of-service. The severity is compounded when ASLR (Address Space Layout Randomization) is disabled or bypassed, removing a key memory protection layer. Additionally, high-severity configuration injection flaws in NGINX Gateway Fabric expose authenticated pathways to further compromise. Because NGINX is one of the most widely deployed web servers globally, the blast radius of these vulnerabilities is enormous. Organizations that lack rapid patching processes for critical internet-facing infrastructure are especially at risk of full system compromise.

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Indicators of Compromise

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

Entities

F5 (vendor)NGINX Plus (product)NGINX Open Source (product)NGINX Gateway Fabric (product)NGINX Instance Manager (product)BIG-IP (product)