OESA-2026-4544: nginx security update

NGINX is a free, open-source, high-performance HTTP server and reverse proxy, as well as an IMAP/POP3 proxy server. Security Fix(es):

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 $requestfilename variable. Alternatively, the same result could be achieved when the $requestfilename 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.(CVE-2026-15176)

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.(CVE-2026-93479)

NGINX Plus and NGINX Open Source have a vulnerability in the ngxhttpcoremodule 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.(CVE-2026-97205)

Description When NGINX Plus or NGINX Open Source is configured with sslsessioncache

shared:name:size

without an explicit sslsessionticketkey file directives to automatically rotate SSL session ticket keys, a remote unauthenticated attacker is able to forge client SSL sessions

in a non-deterministic manner that is beyond the attacker's control. An attacker could leverage this vulnerability to bypass verification of client certificates.

Impact

This vulnerability can lead to the exposure of resources or functionality to unintended actors, possibly providing attackers with access to sensitive information. 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.(CVE-2026-97629)