Ubuntu 20.04 LTS nginx Security Advisory for Critical DoS Vulnerabilities

A security issue affects these releases of Ubuntu and its derivatives: - Ubuntu 20.04 LTS - Ubuntu 18.04 LTS - Ubuntu 16.04 LTS - Ubuntu 14.04 LTS Summary: Several security issues were fixed in nginx. Software Description: - nginx: small, powerful, scalable web/proxy server Details: It was discovered that the nginx ngx_mail_smtp_module module incorrectly handled certain memory operations when doing SMTP authentication. This could possibly result in sensitive information being sent to the authentication server. (CVE-2025-53859) It was discovered that nginx incorrectly handled proxying to upstream TLS servers. An attacker could possibly use this issue to insert plain text data into the response from an upstream proxied server. (CVE-2026-1642) It was discovered that the nginx ngx_mail_auth_http_module module incorrectly handled certain requests. An attacker could possibly use this issue to cause nginx to crash, resulting in a denial of service. (CVE-2026-27651) It was discove...

The problem can be corrected by updating your system to the following package versions: Ubuntu 20.04 LTS libnginx-mod-http-headers-more-filter 1.18.0-0ubuntu1.7+esm1 Available with Ubuntu Pro libnginx-mod-http-lua 1.18.0-0ubuntu1.7+esm1 Available with Ubuntu Pro libnginx-mod-mail 1.18.0-0ubuntu1.7+esm1 Available with Ubuntu Pro libnginx-mod-nchan 1.18.0-0ubuntu1.7+esm1 Available with Ubuntu Pro libnginx-mod-rtmp 1.18.0-0ubuntu1.7+esm1 Available with Ubuntu Pro nginx 1.18.0-0ubuntu1.7+esm1 Available with Ubuntu Pro nginx-core 1.18.0-0ubuntu1.7+esm1 Available with Ubuntu Pro nginx-extras 1.18.0-0ubuntu1.7+esm1 Available with Ubuntu Pro nginx-full 1.18.0-0ubuntu1.7+esm1 Available with Ubuntu Pro nginx-light 1.18.0-0ubuntu1.7+esm1 Available with Ubuntu Pro Ubuntu 18.04 LTS libnginx-mod-http-auth-pam 1.14.0-0ubuntu1.11+esm2 Available with Ubuntu Pro libnginx-mod-http-cache-purge 1.14.0-0ubuntu1.11+esm2 Available with Ubuntu Pro libnginx-mod-http-dav-ext 1.14.0-0ubuntu1.11+esm2 Available with Ubuntu Pro libnginx-mod-http-echo 1.14.0-0ubuntu1.11+esm2 Available with Ubuntu Pro libnginx-mod-http-fancyindex 1.14.0-0ubuntu1.11+esm2 Available with Ubuntu Pro libnginx-mod-http-geoip 1.14.0-0ubuntu1.11+esm2 Available with Ubuntu Pro libnginx-mod-http-headers-more-filter 1.14.0-0ubuntu1.11+esm2 Available with Ubuntu Pro libnginx-mod-http-image-filter 1.14.0-0ubuntu1.11+esm2 Available with Ubuntu Pro libnginx-mod-http-lua 1.14.0-0ubuntu1.11+esm2 Available with Ubuntu Pro libnginx-mod-http-ndk 1.14.0-0ubuntu1.11+esm2 Available with Ubuntu Pro libnginx-mod-http-perl 1.14.0-0ubuntu1.11+esm2 Available with Ubuntu Pro libnginx-mod-http-subs-filter 1.14.0-0ubuntu1.11+esm2 Available with Ubuntu Pro libnginx-mod-http-uploadprogress 1.14.0-0ubuntu1.11+esm2 Available with Ubuntu Pro libnginx-mod-http-upstream-fair 1.14.0-0ubuntu1.11+esm2 Available with Ubuntu Pro libnginx-mod-http-xslt-filter 1.14.0-0ubuntu1.11+esm2 Available with Ubuntu Pro libnginx-mod-mail 1.14.0-0ubuntu1.11+esm2 Available with Ubuntu Pro libnginx-mod-nchan 1.14.0-0ubuntu1.11+esm2 Available with Ubuntu Pro libnginx-mod-rtmp 1.14.0-0ubuntu1.11+esm2 Available with Ubuntu Pro libnginx-mod-stream 1.14.0-0ubuntu1.11+esm2 Available with Ubuntu Pro nginx 1.14.0-0ubuntu1.11+esm2 Available with Ubuntu Pro nginx-core 1.14.0-0ubuntu1.11+esm2 Available with Ubuntu Pro nginx-extras 1.14.0-0ubuntu1.11+esm2 Available with Ubuntu Pro nginx-full 1.14.0-0ubuntu1.11+esm2 Available with Ubuntu Pro nginx-light 1.14.0-0ubuntu1.11+esm2 Available with Ubuntu Pro Ubuntu 16.04 LTS nginx 1.10.3-0ubuntu0.16.04.5+esm7 Available with Ubuntu Pro nginx-core 1.10.3-0ubuntu0.16.04.5+esm7 Available with Ubuntu Pro nginx-extras 1.10.3-0ubuntu0.16.04.5+esm7 Available with Ubuntu Pro nginx-full 1.10.3-0ubuntu0.16.04.5+esm7 Available with Ubuntu Pro nginx-light 1.10.3-0ubuntu0.16.04.5+esm7 Available with Ubuntu Pro Ubuntu 14.04 LTS nginx 1.4.6-1ubuntu3.9+esm6 Available with Ubuntu Pro nginx-common 1.4.6-1ubuntu3.9+esm6 Available with Ubuntu Pro nginx-core 1.4.6-1ubuntu3.9+esm6 Available with Ubuntu Pro nginx-extras 1.4.6-1ubuntu3.9+esm6 Available with Ubuntu Pro nginx-full 1.4.6-1ubuntu3.9+esm6 Available with Ubuntu Pro nginx-light 1.4.6-1ubuntu3.9+esm6 Available with Ubuntu Pro nginx-naxsi 1.4.6-1ubuntu3.9+esm6 Available with Ubuntu Pro In general, a standard system update will make all the necessary changes.

CVE-2025-53859, CVE-2026-1642, CVE-2026-27651, CVE-2026-27654,

CVE-2026-27784, CVE-2026-28753, CVE-2026-32647, CVE-2026-40701,

CVE-2026-42934, CVE-2026-42945, CVE-2026-42946, CVE-2026-9256

Ubuntu Security Notice USN-8375-1

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