NGINX Open Source and NGINX Plus have a vulnerability in the ngx_mail_smtp_module that might allow an unauthenticated attacker to over-read NGINX SMTP authentication process memory; as a result, the server side may leak arbitrary bytes sent in a request to the authentication server. This issue happens during the NGINX SMTP authentication process and requires the attacker to make preparations against the target system to extract the leaked data. The issue affects NGINX only if (1) it is built with the ngx_mail_smtp_module, (2) the smtp_auth directive is configured with method "none," and (3) the authentication server returns the "Auth-Wait" response header. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

According to its Server response header, the installed version of nginx is from 0.7.22 to 1.29.0. It is, therefore, affected by a buffer over-read vulnerability in the ngx_mail_smtp_module that might allow an unauthenticated attacker to over-read NGINX SMTP authentication process memory; as a result, the server side may leak arbitrary bytes sent in a request to the authentication server.

Note that the scanner has not tested for these issues but has instead relied only on the application's self-reported version number.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - NGINX Open Source and NGINX Plus have a vulnerability in the ngx_mail_smtp_module that might allow an     unauthenticated attacker to over-read NGINX SMTP authentication process memory; as a result, the server     side may leak arbitrary bytes sent in a request to the authentication server. This issue happens during     the NGINX SMTP authentication process and requires the attacker to make preparations against the target     system to extract the leaked data. The issue affects NGINX only if (1) it is built with the     ngx_mail_smtp_module, (2) the smtp_auth directive is configured with method none, and (3) the     authentication server returns the Auth-Wait response header. Note: Software versions which have reached     End of Technical Support (EoTS) are not evaluated. (CVE-2025-53859)

Note that Nessus relies on the presence of the package as reported by the vendor.

The remote Ubuntu 22.04 LTS / 24.04 LTS / 25.04 host has packages installed that are affected by a vulnerability as referenced in the USN-7715-1 advisory.

    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.

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

According to its Sever response header, the installed version of nginx is 0.7.22 prior to 1.29.1. It is, therefore, affected by the following issue :

  - NGINX Open Source and NGINX Plus have a vulnerability in the ngx_mail_smtp_module that might allow an     unauthenticated attacker to over-read NGINX SMTP authentication process memory; as a result, the server     side may leak arbitrary bytes sent in a request to the authentication server. This issue happens during     the NGINX SMTP authentication process and requires the attacker to make preparations against the target     system to extract the leaked data. The issue affects NGINX only if (1) it is built with the     ngx_mail_smtp_module, (2) the smtp_auth directive is configured with method none, and (3) the     authentication server returns the Auth-Wait response header. Note: Software versions which have reached     End of Technical Support (EoTS) are not evaluated. (CVE-2025-53859)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

An update of the nginx package has been released.

The version of nginx installed on the remote host is prior to 1.28.0-1. It is, therefore, affected by a vulnerability as referenced in the ALAS2NGINX1-2025-009 advisory.

    NGINX Open Source and NGINX Plus have a vulnerability in the ngx_mail_smtp_module that might allow an     unauthenticated attacker to over-read NGINX SMTP authentication process memory; as a result, the server     side may leak arbitrary bytes sent in a request to the authentication server. This issue happens during     the NGINX SMTP authentication process and requires the attacker to make preparations against the target     system to extract the leaked data. The issue affects NGINX only if (1) it is built with the     ngx_mail_smtp_module, (2) the smtp_auth directive is configured with method none, and (3) the     authentication server returns the Auth-Wait response header.Note: Software versions which have reached     End of Technical Support (EoTS) are not evaluated. (CVE-2025-53859)

Tenable has extracted the preceding description block directly from the tested product security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

It is, therefore, affected by a vulnerability as referenced in the ALAS2023-2025-1152 advisory.

    NGINX Open Source and NGINX Plus have a vulnerability in the ngx_mail_smtp_module that might allow an     unauthenticated attacker to over-read NGINX SMTP authentication process memory; as a result, the server     side may leak arbitrary bytes sent in a request to the authentication server. This issue happens during     the NGINX SMTP authentication process and requires the attacker to make preparations against the target     system to extract the leaked data. The issue affects NGINX only if (1) it is built with the     ngx_mail_smtp_module, (2) the smtp_auth directive is configured with method none, and (3) the     authentication server returns the Auth-Wait response header.Note: Software versions which have reached     End of Technical Support (EoTS) are not evaluated. (CVE-2025-53859)

Tenable has extracted the preceding description block directly from the tested product security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The version of FreeBSD installed on the remote host is prior to tested version. It is, therefore, affected by a vulnerability as referenced in the eb03714d-79f0-11f0-b4c1-ac5afc632ba3 advisory.

    F5 reports:
    NGINX Open Source and NGINX Plus have a vulnerability in the               ngx_mail_smtp_module that might allow an unauthenticated attacker to               over-read NGINX SMTP authentication process memory; as a result, the               server side may leak arbitrary bytes sent in a request to the               authentication server.  This issue happens during the NGINX SMTP               authentication process and requires the attacker to make preparations               against the target system to extract the leaked data.  The issue               affects NGINX only if (1) it is built with the ngx_mail_smtp_module,               (2) the smtp_auth directive is configured with method none,               and (3) the authentication server returns the Auth-Wait response               header.

Tenable has extracted the preceding description block directly from the FreeBSD security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

ID	Name	Product	Family	Severity
114954	Nginx 0.7.22 < 1.29.1 Buffer Over-read	Web App Scanning	Component Vulnerability	medium
260005	Linux Distros Unpatched Vulnerability : CVE-2025-53859	Nessus	Misc.	medium
258037	Ubuntu 22.04 LTS / 24.04 LTS / 25.04 : nginx vulnerability (USN-7715-1)	Nessus	Ubuntu Local Security Checks	medium
253588	nginx 0.7.22 < 1.29.1 Information Disclosure	Nessus	Web Servers	medium
252968	Photon OS 4.0: Nginx PHSA-2025-4.0-0852	Nessus	PhotonOS Local Security Checks	medium
252967	Photon OS 5.0: Nginx PHSA-2025-5.0-0596	Nessus	PhotonOS Local Security Checks	medium
252306	Amazon Linux 2 : nginx, --advisory ALAS2NGINX1-2025-009 (ALASNGINX1-2025-009)	Nessus	Amazon Linux Local Security Checks	medium
251383	Amazon Linux 2023 : nginx, nginx-all-modules, nginx-core (ALAS2023-2025-1152)	Nessus	Amazon Linux Local Security Checks	medium
250297	FreeBSD : nginx -- worker process memory disclosure (eb03714d-79f0-11f0-b4c1-ac5afc632ba3)	Nessus	FreeBSD Local Security Checks	medium

Detections

Analytics

CVE-2025-53859

medium

Tenable Plugins

medium

medium

medium

medium

medium

medium

medium

medium

medium