CVE-2023-51764

Postfix through 3.8.5 allows SMTP smuggling unless configured with smtpd_data_restrictions=reject_unauth_pipelining and smtpd_discard_ehlo_keywords=chunking (or certain other options that exist in recent versions). Remote attackers can use a published exploitation technique to inject e-mail messages with a spoofed MAIL FROM address, allowing bypass of an SPF protection mechanism. This occurs because Postfix supports <LF>.<CR><LF> but some other popular e-mail servers do not. To prevent attack variants (by always disallowing <LF> without <CR>), a different solution is required, such as the smtpd_forbid_bare_newline=yes option with a Postfix minimum version of 3.5.23, 3.6.13, 3.7.9, 3.8.4, or 3.9.

Postfix through 3.8.5 allows SMTP smuggling unless configured with smtpd_data_restrictions=reject_unauth_pipelining and smtpd_discard_ehlo_keywords=chunking (or certain other options that exist in recent versions). Remote attackers can use a published exploitation technique to inject e-mail messages with a spoofed MAIL FROM address, allowing bypass of an SPF protection mechanism. This occurs because Postfix supports <LF>.<CR><LF> but some other popular e-mail servers do not. To prevent attack variants (by always disallowing <LF> without <CR>), a different solution is required, such as the smtpd_forbid_bare_newline=yes option with a Postfix minimum version of 3.5.23, 3.6.13, 3.7.9, 3.8.4, or 3.9.

Postfix hasta 3.8.4 permite el contrabando SMTP a menos que se configure con smtpd_data_restrictions=reject_unauth_pipelining (u otras opciones que existen en versiones recientes). Los atacantes remotos pueden utilizar una técnica de explotación publicada para inyectar mensajes de correo electrónico que parecen originarse en el servidor Postfix, lo que permite omitir un mecanismo de protección SPF. Esto ocurre porque Postfix admite . pero algunos otros servidores de correo electrónico populares no lo hacen. Para evitar variantes de ataque (al no permitir siempre sin ), se requiere una solución diferente: la opción smtpd_forbid_bare_newline=yes con una versión mínima de Postfix de 3.5.23, 3.6.13, 3.7.9, 3.8.4, o 3.9.