{"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\/fr\/blog\/news\/uyazvimost-v-telnetd-pozvolyayushhaya-podklyuchitsya-s-pravami-root-bez-autentifikaczii","title":{"rendered":"Vuln\u00e9rabilit\u00e9 dans telnetd permettant de se connecter avec des droits root sans authentification","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Une vuln\u00e9rabilit\u00e9 a \u00e9t\u00e9 identifi\u00e9e dans le serveur telnetd de la collection GNU InetUtils, permettant de se connecter en tant qu'utilisateur quelconque, y compris l'utilisateur root, sans v\u00e9rification de mot de passe. Aucun identifiant CVE n'a encore \u00e9t\u00e9 attribu\u00e9. La vuln\u00e9rabilit\u00e9 appara\u00eet \u00e0 partir de la version InetUtils 1.9.3 (2015) et demeure non corrig\u00e9e dans la version actuelle 2.7.0. Un correctif est disponible sous forme de patchs (1, 2). <\/p>\n

Le probl\u00e8me vient du fait que pour v\u00e9rifier le mot de passe, le processus telnetd appelle l'utilitaire \u00ab \/usr\/bin\/login \u00bb, en passant comme argument le nom d'utilisateur fourni par le client lors de la connexion \u00e0 serveur<\/a>. L'utilitaire \u00ab login \u00bb prend en charge l'option \u00ab -f \u00bb, permettant de se connecter sans effectuer d'authentification (on suppose que cette option est utilis\u00e9e lorsque l'utilisateur a d\u00e9j\u00e0 \u00e9t\u00e9 v\u00e9rifi\u00e9). Ainsi, si on r\u00e9ussit \u00e0 substituer l'option \u00ab -f \u00bb dans le nom d'utilisateur, on peut se connecter sans v\u00e9rifier le mot de passe. <\/p>\n

Lors d'une connexion normale, il n'est pas possible d'utiliser un nom d'utilisateur tel que \u00ab -f root \u00bb, mais telnet poss\u00e8de un mode de connexion automatique, activ\u00e9 par l'option \u00ab -a \u00bb. Dans ce mode, le nom d'utilisateur n'est pas pris dans la ligne de commande, mais est transmis par la variable d'environnement USER. Lors de l'appel de l'utilitaire login, la valeur de cette variable d'environnement \u00e9tait substitu\u00e9e sans v\u00e9rification suppl\u00e9mentaire et sans \u00e9chappement de caract\u00e8res sp\u00e9ciaux. Ainsi, pour se connecter en tant qu'utilisateur root, il suffit de d\u00e9finir la variable d'environnement USER avec la valeur \u00ab -f root \u00bb et de se connecter au serveur telnet en sp\u00e9cifiant l'option \u00ab -a \u00bb : $ USER='-f root' telnet -a nom_du_serveur <\/p>\n

Le changement ayant conduit \u00e0 la vuln\u00e9rabilit\u00e9 a \u00e9t\u00e9 ajout\u00e9 au code de telnetd en mars 2015 et \u00e9tait li\u00e9 \u00e0 la solution d'un probl\u00e8me emp\u00eachant de d\u00e9terminer le nom d'utilisateur en mode autologin sans authentification dans Kerberos. Pour r\u00e9soudre cela, la prise en charge du passage du nom d'utilisateur pour le mode autologin a \u00e9t\u00e9 ajout\u00e9e via une variable d'environnement, mais la v\u00e9rification de la validit\u00e9 du nom d'utilisateur \u00e0 partir de la variable d'environnement a \u00e9t\u00e9 oubli\u00e9e.
\n
Source : 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. 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