AS-2026-010: Nginx

2026-05-19

Statement

F5 Networks has issued the security advisory, pointing out that the Nginx web server, which uses an asynchronous event-driven framework, has a security vulnerability, CVE-2026-42945, which occurs in the ngx_http_rewrite_module component.

F5 Networks announced multiple security vulnerabilities that have been fixed in the latest release of Nginx 1.30.1.

CVE-2026-42945, CVE-2026-42946, CVE-2026-40701, CVE-2026-42934 and CVE-2026-40460 will affect ASUSTOR products with Nginx 1.18 or 1.24 installed.

• Nginx 1.30.1 will be released to resolve the issues as soon as possible.

Affected Products

Detail

• CVE-2026-42945
  • Severity: Critical
  • CVSS4 Base Score: 9.2
  • CVSS4 Vector: CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
  • NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_rewrite_module module. This vulnerability exists when the rewrite directive is followed by a rewrite, if, or set directive and an unnamed Perl-Compatible Regular Expression (PCRE) capture (for example, $1, $2) with a replacement string that includes a question mark (?). An unauthenticated attacker along with conditions beyond its 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, for systems with Address Space Layout Randomization (ASLR ) disabled, code execution is possible. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.
• CVE-2026-42946
  • Severity: High
  • CVSS4 Base Score: 8.3
  • CVSS4 Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:L/SC:N/SI:N/SA:N
  • A vulnerability exists in the ngx_http_scgi_module and ngx_http_uwsgi_module modules that may result in excessive memory allocation or an over-read of data. When scgi_pass or uwsgi_pass is configured, an unauthenticated attacker with man-in-the-middle (MITM) ability to control responses from an upstream server may be able to read the memory of the NGINX worker process or restart it. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.
• CVE-2026-40701
  • Severity: Medium
  • CVSS4 Base Score: 6.3
  • CVSS4 Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N
  • NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_ssl_module module when the ssl_verify_client directive is set to "on" or "optional," and the ssl_ocsp directive is set to "on" or the leaf parameters are configured with a resolver. With this configuration, an unauthenticated attacker can send requests along with conditions beyond its control that may cause a heap-use-after-free error in the NGINX worker process. This vulnerability may result in limited modification of data or the NGINX worker process restarting. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.
• CVE-2026-42934
  • Severity: Medium
  • CVSS4 Base Score: 6.3
  • CVSS4 Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N
  • NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_charset_module module. When charset, source_charset, and charset_map and proxy_pass with disabled buffering ("off") directives are configured, unauthenticated attackers can send requests that with conditions beyond the attackers' control to cause a heap buffer over-read in the NGINX worker process, leading to limited disclosure of memory or a restart. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.
• CVE-2026-40460
  • Severity: Medium
  • CVSS4 Base Score: 6.9
  • CVSS4 Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N
  • When NGINX Plus or NGINX Open Source are configured to use the HTTP/3 QUIC module, an attacker may be able to spoof their source IP address allowing for bypass of authorization or bypass of rate limiting. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

Reference

• CVE-2026-42945
• CVE-2026-42946
• CVE-2026-40701
• CVE-2026-42934
• CVE-2026-40460
• F5 security advisory: NGINX ngx_http_rewrite_module vulnerability CVE-2026-42945
• Nginx security advisories

Revision