{"id":154530,"date":"2026-01-20T23:11:56","date_gmt":"2026-01-20T21:11:56","guid":{"rendered":"https:\/\/prohoster.info\/blog\/novosti-interneta\/uyazvimost-v-telnetd-pozvolyayushhaya-podklyuchitsya-s-pravami-root-bez-autentifikaczii"},"modified":"2026-01-20T23:11:56","modified_gmt":"2026-01-20T21:11:56","slug":"uyazvimost-v-telnetd-pozvolyayushhaya-podklyuchitsya-s-pravami-root-bez-autentifikaczii","status":"publish","type":"post","link":"https:\/\/prohoster.info\/es\/blog\/news\/uyazvimost-v-telnetd-pozvolyayushhaya-podklyuchitsya-s-pravami-root-bez-autentifikaczii","title":{"rendered":"Vulnerabilidad en telnetd que permite conectarse con privilegios de root sin autenticaci\u00f3n","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Se ha detectado una vulnerabilidad en el servidor telnetd del conjunto GNU InetUtils, que permite conectarse como cualquier usuario, incluyendo el usuario root, sin verificar la contrase\u00f1a. A\u00fan no se ha asignado un identificador CVE. La vulnerabilidad se manifiesta a partir de la versi\u00f3n InetUtils 1.9.3 (2015) y permanece sin corregirse en la versi\u00f3n actual 2.7.0. La correcci\u00f3n est\u00e1 disponible en forma de parches (1, 2). <\/p>\n

El problema se debe a que el proceso telnetd llama a la utilidad para verificar la contrase\u00f1a, pasando como argumento el nombre de usuario indicado por el cliente al conectarse a servidor<\/a>. La utilidad admite la opci\u00f3n , que permite iniciar sesi\u00f3n sin realizar la autenticaci\u00f3n (se asume que esta opci\u00f3n se utiliza cuando el usuario ya ha pasado la verificaci\u00f3n). Por lo tanto, si se logra insertar la opci\u00f3n en el nombre de usuario, se puede conectarse sin verificar la contrase\u00f1a. <\/p>\n

En una conexi\u00f3n normal no se puede usar un nombre de usuario del tipo , pero en telnet hay un modo de conexi\u00f3n autom\u00e1tica que se activa con la opci\u00f3n . En este modo, el nombre de usuario no se toma de la l\u00ednea de comandos, sino que se pasa a trav\u00e9s de la variable de entorno USER. Al llamar a la utilidad login, el valor de esta variable de entorno se insertaba sin verificaci\u00f3n adicional y sin escape de caracteres especiales. Por lo tanto, para conectarse como usuario root, es suficiente establecer en la variable de entorno USER el valor y conectarse al servidor telnet, especificando la opci\u00f3n : $ USER='-f root' telnet -a nombre_del_servidor <\/p>\n

El cambio que condujo a la vulnerabilidad se a\u00f1adi\u00f3 al c\u00f3digo de telnetd en marzo de 2015 y estuvo relacionado con la resoluci\u00f3n de un problema que imped\u00eda identificar el nombre de usuario en el modo autologin sin realizar autenticaci\u00f3n en Kerberos. Como soluci\u00f3n, se agreg\u00f3 soporte para pasar el nombre de usuario para el modo autologin a trav\u00e9s de una variable de entorno, pero olvidaron agregar la verificaci\u00f3n de la validez del nombre de usuario de la variable de entorno.
\n
Fuente: opennet.ru<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

\u0412 \u0441\u0435\u0440\u0432\u0435\u0440\u0435 telnetd \u0438\u0437 \u043d\u0430\u0431\u043e\u0440\u0430 GNU InetUtils \u0432\u044b\u044f\u0432\u043b\u0435\u043d\u0430 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c, \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u044e\u0449\u0430\u044f \u043f\u043e\u0434\u043a\u043b\u044e\u0447\u0438\u0442\u044c\u0441\u044f \u043f\u043e\u0434 \u043b\u044e\u0431\u044b\u043c \u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u0442\u0435\u043b\u0435\u043c, \u0432\u043a\u043b\u044e\u0447\u0430\u044f \u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u0442\u0435\u043b\u044f root, \u0431\u0435\u0437 \u043f\u0440\u043e\u0432\u0435\u0440\u043a\u0438 \u043f\u0430\u0440\u043e\u043b\u044f. CVE-\u0438\u0434\u0435\u043d\u0442\u0438\u0444\u0438\u043a\u0430\u0442\u043e\u0440 \u043f\u043e\u043a\u0430 \u043d\u0435 \u043f\u0440\u0438\u0441\u0432\u043e\u0435\u043d. \u0423\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c \u043f\u0440\u043e\u044f\u0432\u043b\u044f\u0435\u0442\u0441\u044f \u043d\u0430\u0447\u0438\u043d\u0430\u044f \u0441 \u0432\u0435\u0440\u0441\u0438\u0438 InetUtils 1.9.3 (2015 \u0433\u043e\u0434) \u0438 \u043e\u0441\u0442\u0430\u0451\u0442\u0441\u044f \u043d\u0435\u0438\u0441\u043f\u0440\u0430\u0432\u043b\u0435\u043d\u043d\u043e\u0439 \u0432 \u0430\u043a\u0442\u0443\u0430\u043b\u044c\u043d\u043e\u043c \u0432\u044b\u043f\u0443\u0441\u043a\u0435 2.7.0. \u0418\u0441\u043f\u0440\u0430\u0432\u043b\u0435\u043d\u0438\u0435 \u0434\u043e\u0441\u0442\u0443\u043f\u043d\u043e \u0432 \u0444\u043e\u0440\u043c\u0435 \u043f\u0430\u0442\u0447\u0435\u0439 (1, 2). \u041f\u0440\u043e\u0431\u043b\u0435\u043c\u0430 \u0432\u044b\u0437\u0432\u0430\u043d\u0430 \u0442\u0435\u043c, 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