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F5 patches critical code execution flaws in NGINX web servers

Feeds.4Sysops •IT News • June 18, 2026

F5 has released out-of-band security updates to address multiple vulnerabilities in the NGINX web server. The patches resolve two critical-severity flaws, CVE-2026-42530 and CVE-2026-42055, which could allow remote attackers to execute arbitrary code. These vulnerabilities affect NGINX systems with non-default configurations and can trigger a denial-of-service condition or worker process restart. Source

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F5 Issues Critical Patches for NGINX Vulnerabilities Allowing Remote Code Execution On June 17, 2026, F5 released emergency patches for two critical vulnerabilities in NGINX, CVE-2026-42530 and CVE-2026-42055. These vulnerabilities affect NGINX Open Source, NGINX Plus, and related products, allowing unauthenticated remote attackers to execute arbitrary code and cause denial-of-service (DoS) attacks. CVE-2026-42530 is a use-after-free vulnerability in the HTTP/3 module, while CVE-2026-42055 is a heap buffer overflow in the HTTP/2 and gRPC modules. Both vulnerabilities have a CVSS v4.0 score of 9.2, indicating their critical severity. F5 advises immediate patching, as exploitation could occur rapidly. The vulnerabilities impact a significant portion of the web, with NGINX running on approximately 38% of active websites worldwide. Patches are available for affected versions, and interim mitigations are suggested for those unable to update immediately. 16 sources 80

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F5 patches critical code execution flaws in NGINX web servers

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