USN-8354-1: nginx vulnerabilities

Publication date

1 June 2026

Overview

Several security issues were fixed in nginx.


Packages

  • nginx - small, powerful, scalable web/proxy server

Details

It was discovered that nginx did not properly validate source addresses in
the HTTP/3 QUIC module. A remote attacker could possibly use this issue to
bypass authorization checks or rate limiting. This issue only affected
Ubuntu 25.04 and Ubuntu 25.10. (CVE-2026-40460)

It was discovered that nginx contained a use-after-free vulnerability in
the ngx_http_ssl_module module when client certificate verification and
OCSP validation were enabled. A remote attacker could use this issue to
cause nginx to crash, resulting in a denial of service, or possibly modify
data in memory. (CVE-2026-40701)

It was discovered that nginx did not properly handle certain proxied
responses in the ngx_http_charset_module module. A remote attacker could
possibly use this issue to obtain sensitive information or cause nginx to
crash, resulting in a denial of service. (

It was discovered that nginx did not properly validate source addresses in
the HTTP/3 QUIC module. A remote attacker could possibly use this issue to
bypass authorization checks or rate limiting. This issue only affected
Ubuntu 25.04 and Ubuntu 25.10. (CVE-2026-40460)

It was discovered that nginx contained a use-after-free vulnerability in
the ngx_http_ssl_module module when client certificate verification and
OCSP validation were enabled. A remote attacker could use this issue to
cause nginx to crash, resulting in a denial of service, or possibly modify
data in memory. (CVE-2026-40701)

It was discovered that nginx did not properly handle certain proxied
responses in the ngx_http_charset_module module. A remote attacker could
possibly use this issue to obtain sensitive information or cause nginx to
crash, resulting in a denial of service. (CVE-2026-42934)

It was discovered that nginx did not properly process certain SCGI and
uWSGI responses. An attacker able to perform a machine-in-the-middle attack
could possibly use this issue to obtain sensitive information or cause
nginx to crash, resulting in a denial of service. (CVE-2026-42946)

It was discovered that nginx incorrectly handled certain rewrite rules in
the ngx_http_rewrite_module module. A remote attacker could use this issue
to cause nginx to crash, resulting in a denial of service, or possibly
execute arbitrary code. (CVE-2026-9256)


Update instructions

In general, a standard system update will make all the necessary changes.

Learn more about how to get the fixes.

The problem can be corrected by updating your system to the following package versions:


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