{"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\/it\/blog\/news\/uyazvimost-v-telnetd-pozvolyayushhaya-podklyuchitsya-s-pravami-root-bez-autentifikaczii","title":{"rendered":"Vulnerabilit\u00e0 in telnetd che consente l'accesso con diritti di root senza autenticazione","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

\u00c8 stata identificata una vulnerabilit\u00e0 nel server telnetd del pacchetto GNU InetUtils, che consente di connettersi come qualsiasi utente, incluso l'utente root, senza controllo della password. Non \u00e8 ancora stato assegnato alcun identificativo CVE. La vulnerabilit\u00e0 si manifesta a partire dalla versione InetUtils 1.9.3 (2015) ed \u00e8 rimasta non corretta nella attuale versione 2.7.0. Una correzione \u00e8 disponibile sotto forma di patch (1, 2). <\/p>\n

Il problema \u00e8 causato dal fatto che per la verifica della password il processo telnetd chiama l'utilit\u00e0 \u00ab\/usr\/bin\/login\u00bb, passando come argomento il nome utente specificato dal cliente al momento della connessione a server<\/a>. L'utilit\u00e0 \u00ablogin\u00bb supporta l'opzione \u00ab-f\u00bb, che consente di accedere senza eseguire l'autenticazione (si presume che questa opzione sia utilizzata quando l'utente ha gi\u00e0 superato la verifica). Pertanto, se si riesce a includere l'opzione \u00ab-f\u00bb nel nome utente, \u00e8 possibile connettersi senza verifica della password. <\/p>\n

Durante una normale connessione non \u00e8 possibile utilizzare un nome utente come \u00ab-f root\u00bb, ma in telnet c'\u00e8 una modalit\u00e0 di connessione automatica, attivata dall'opzione \u00ab-a\u00bb. In questa modalit\u00e0, il nome utente non viene preso dalla riga di comando, ma viene passato tramite la variabile d'ambiente USER. Quando viene chiamata l'utilit\u00e0 login, il valore di questa variabile d'ambiente viene utilizzato senza ulteriori controlli e senza l'escaping dei caratteri speciali. Pertanto, per connettersi come utente root \u00e8 sufficiente impostare nella variabile d'ambiente USER il valore \u00ab-f root\u00bb e connettersi al server telnet specificando l'opzione \u00ab-a\u00bb: $ USER='-f root' telnet -a nome_server <\/p>\n

La modifica che ha portato alla vulnerabilit\u00e0 \u00e8 stata aggiunta al codice telnetd nel marzo 2015 ed era correlata alla risoluzione di un problema che non permetteva di determinare il nome utente in modalit\u00e0 autologin senza autenticazione in Kerberos. Come soluzione \u00e8 stata aggiunta la possibilit\u00e0 di passare il nome utente per la modalit\u00e0 autologin tramite una variabile di ambiente, ma si sono dimenticati di aggiungere il controllo corretto del nome utente dalla variabile di ambiente.
\n
Fonte: 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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