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F5 Issues Critical Patches for NGINX Vulnerabilities Allowing Remote Code Execution

F5 Issues Critical Patches for NGINX Vulnerabilities Allowing Remote Code Execution

First seen 18 Jun 2026, 12:57 UTC • •
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ThreatCluster AI
ThreatCluster •June 19, 2026 at 12:27 UTC

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.

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