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F5 Releases Security Advisory for Critical Vulnerabilities in NGINX Plus and NGINX Open Source

The advisory addresses three vulnerabilities that could allow an unauthenticated remote attacker to cause denial-of-service or potentially achieve remote code execution on affected systems

Threat ID:
CC-4872
Threat Severity:
Medium
Published:
19 October 2026 1:53 PM
Report a cyber attack: call 0300 303 5222 or email [email protected]

Summary

The advisory addresses three vulnerabilities that could allow an unauthenticated remote attacker to cause denial-of-service or potentially achieve remote code execution on affected systems

Threat details

Introduction

F5 has released a security advisory to address multiple critical vulnerabilities in NGINX Plus and NGINX Open Source. Successful exploitation of CVE-2026-15176, CVE-2026-93479, or CVE-2026-97205 could allow an unauthenticated remote attacker to cause denial-of-service or potentially achieve remote code execution on affected systems.

  • CVE-2026-15176 - 'Heap-based Buffer Overflow' vulnerability - CVSSv4 score: 9.2
  • CVE-2026-93479 - 'Heap-based Buffer Overflow' vulnerability - CVSSv4 score: 9.2
  • CVE-2026-97205 - 'Use After Free' vulnerability - CVSSv4 score: 9.2

Note: Attackers could execute code on systems with Address Space Layout Randomisation (ASLR) disabled or when the attacker can bypass ASLR.

Remediation advice

Affected organisations are encouraged to review F5 advisory K000163408 and apply the relevant updates as soon as possible. Organisations should additionally identify NGINX deployments using regex-based map directives and ensure use of named captures only when using the map directive.

Definitive source of threat updates

CVE Vulnerabilities

Status Published

CVE-2026-15176

A vulnerability exists in NGINX Plus and NGINX Open Source when a location is configured that uses the alias directive together with rewrite and a set or return directive referencing the $request_filename variable. Alternatively, the same result could be achieved when the $request_filename variable is used in an access log format directive. An unauthenticated attacker along with conditions beyond their control can exploit this vulnerability by sending crafted HTTP requests. This may cause a heap buffer overflow in the NGINX worker process leading to a restart. Additionally, attackers can execute code on systems with Address Space Layout Randomization (ASLR) disabled or when the attacker can bypass ASLR. Impact: This vulnerability may allow remote attackers to cause a denial-of-service (DoS) on the NGINX system or to possibly trigger a code execution. There is no control plane exposure; this is a data plane issue only. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.
Status Published

CVE-2026-93479

A vulnerability exists in NGINX Plus and NGINX Open Source when a map directive uses regex matching and the root directive or access log format references the map's regex capture variables before referencing the map output variable. Alternatively, the same result could be achieved by using a non-cacheable variable in a string expression under certain conditions. An unauthenticated attacker along with conditions beyond their control can exploit this vulnerability by sending crafted HTTP requests. This may cause a heap buffer overflow in the NGINX worker process leading to a restart. Additionally, attackers can execute code on systems with Address Space Layout Randomization (ASLR) disabled or when the attacker can bypass ASLR. Impact:  This vulnerability may allow remote attackers to cause a denial-of-service (DoS) on the NGINX system or to possibly trigger a code execution. There is no control plane exposure; this is a data plane issue only. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.
Status Published

CVE-2026-97205

NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_core_module module. When asynchronous file I/O (AIO) is enabled in certain configurations, processing a Server Side Includes (SSI) page containing “include virtual” commands may trigger a Use-After-Free (UAF) in the NGINX worker process. This may cause memory corruption or a worker process crash. Additionally, attackers can execute code on systems with Address Space Layout Randomization (ASLR) disabled or when the attacker can bypass ASLR. Impact: This vulnerability may allow remote attackers to cause a denial-of-service (DoS) on the NGINX system, corrupt its memory, or possibly trigger code execution. There is no control plane exposure; this is a data plane issue only. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

Last edited: 19 October 2026 1:53 pm