CVE-2025-53859

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.

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.

NGINX is a free, open-source, high-performance HTTP server and reverse proxy, as well as an IMAP/POP3 proxy server.

Security Fix(es):

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)

NGINX is a free, open-source, high-performance HTTP server and reverse proxy, as well as an IMAP/POP3 proxy server.

Security Fix(es):

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)

NGINX is a free, open-source, high-performance HTTP server and reverse proxy, as well as an IMAP/POP3 proxy server.

Security Fix(es):

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)

NGINX is a free, open-source, high-performance HTTP server and reverse proxy, as well as an IMAP/POP3 proxy server.

Security Fix(es):

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)

NGINX is a free, open-source, high-performance HTTP server and reverse proxy, as well as an IMAP/POP3 proxy server.

Security Fix(es):

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)

NGINX is a free, open-source, high-performance HTTP server and reverse proxy, as well as an IMAP/POP3 proxy server.

Security Fix(es):

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.(CVE-2025-53859)

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.

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.

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.

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.

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: fix buffer over-read in the SMTP authentication path that could disclose worker process memory to the authentication server
• CVE-2026-28753: validate host names resolved from the client address to prevent header injection into auth_http and XCLIENT requests
• CVE-2026-40701: fix use-after-free by cancelling a pending OCSP responder resolve when the client connection is closed
• CVE-2026-42934: fix buffer over-read in the charset filter when a UTF-8 sequence is split across several buffers
• CVE-2026-48142: fix remaining buffer over-read in the charset filter on invalid UTF-8 sequences
• CVE-2026-42946: reset the parsing state and restore the buffer position after an unrecognized upstream status line in the scgi and uwsgi modules

• CVE-2026-40701: fix resolver use-after-free in OCSP; the resolve context was leaked when a client SSL connection was terminated while resolving an OCSP responder, so completion of the resolve touched freed memory
• CVE-2025-53859: fix buffer over-read in ngx_mail_smtp_module; login and password storage could be left in an inconsistent state after base64 decoding errors in the plain/login/cram-md5 auth methods
• CVE-2026-28753: validate the host name resolved from the client address against the character set of RFC 1034 section 3.5, preventing CRLF injection into auth_http and smtp proxy requests
• CVE-2026-42934: fix buffer over-read in ngx_http_charset_module recode_from_utf8(); pass the saved byte count rather than the last saved index to ngx_utf8_decode() and advance past the whole saved sequence on invalid UTF-8

It was discovered that nginx contains a security issue in the ngx_mail_smtp_module which might allow an attacker to cause buffer over-read potentially resulting in sensitive information leak in a HTTP request to the authentication server (CVE-2025-53859).

These are all security issues fixed in the nginx-1.29.1-1.1 package on the GA media of openSUSE Tumbleweed.

This update for nginx fixes the following issues:

• CVE-2025-53859: the server side may leak arbitrary bytes during the NGINX SMTP authentication process (bsc#1248070).
• CVE-2025-23419: session resumption can bypass client certificate authentication requirements using TLSv1.3 (bsc#1236851).

This update for nginx fixes the following issues:

• CVE-2025-53859: the server side may leak arbitrary bytes during the NGINX SMTP authentication process (bsc#1248070).
• CVE-2025-23419: session resumption can bypass client certificate authentication requirements using TLSv1.3 (bsc#1236851).

This update for nginx fixes the following issues:

• CVE-2025-53859:�the server side may leak arbitrary bytes during the NGINX SMTP authentication process (bsc#1248070).
• CVE-2025-23419: session resumption can bypass client certificate authentication requirements using TLSv1.3 (bsc#1236851).

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.

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 discovered that the nginx ngx_http_dav_module module incorrectly handled certain destination URIs. An attacker could use this issue to cause nginx to crash, resulting in a denial of service, or possibly modify source or destination names outside of the document root. (CVE-2026-27654)

It was discovered that the nginx ngx_http_mp4_module module incorrectly handled certain MP4 files. An attacker could use this issue to cause nginx to crash, resulting in a denial of service, or possibly execute arbitrary code. (CVE-2026-27784, CVE-2026-32647)

It was discovered that the nginx ngx_mail_smtp_module module incorrectly handled certain CRLF sequences. An attacker could possibly use this issue to inject arbitrary SMTP headers. (CVE-2026-28753)

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 the nginx ngx_http_rewrite_module component incorrectly handled certain rewrite directives. A remote attacker could use this issue to cause nginx to crash, resulting in a denial of service, or possibly execute arbitrary code. (CVE-2026-42945)

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)