{"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\/pt\/blog\/news\/uyazvimost-v-telnetd-pozvolyayushhaya-podklyuchitsya-s-pravami-root-bez-autentifikaczii","title":{"rendered":"Vulnerabilidade no telnetd que permite conex\u00e3o com privil\u00e9gios de root sem autentica\u00e7\u00e3o","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Uma vulnerabilidade foi identificada no servidor telnetd do conjunto GNU InetUtils, permitindo a conex\u00e3o com qualquer usu\u00e1rio, incluindo o usu\u00e1rio root, sem verifica\u00e7\u00e3o de senha. O identificador CVE ainda n\u00e3o foi atribu\u00eddo. A vulnerabilidade se manifesta a partir da vers\u00e3o InetUtils 1.9.3 (2015) e permanece n\u00e3o corrigida na vers\u00e3o atual 2.7.0. A corre\u00e7\u00e3o est\u00e1 dispon\u00edvel na forma de patches (1, 2). <\/p>\n

O problema \u00e9 causado pelo fato de que, para verificar a senha, o processo telnetd chama a ferramenta \"\\\/usr\\\/bin\\\/login\", passando como argumento o nome de usu\u00e1rio fornecido pelo cliente ao se conectar a servidor<\/a>. A ferramenta \"login\" suporta a op\u00e7\u00e3o \"-f\", que permite fazer login sem autentica\u00e7\u00e3o (presume-se que essa op\u00e7\u00e3o \u00e9 usada quando o usu\u00e1rio j\u00e1 passou pela verifica\u00e7\u00e3o). Assim, se conseguir inserir a op\u00e7\u00e3o \"-f\" no nome de usu\u00e1rio, \u00e9 poss\u00edvel se conectar sem verificar a senha. <\/p>\n

Na conex\u00e3o normal, n\u00e3o \u00e9 poss\u00edvel usar um nome de usu\u00e1rio como \"-f root\", mas o telnet possui um modo de conex\u00e3o autom\u00e1tica, ativado pela op\u00e7\u00e3o \"-a\". Neste modo, o nome de usu\u00e1rio n\u00e3o \u00e9 retirado da linha de comando, mas passado atrav\u00e9s da vari\u00e1vel de ambiente USER. Ao chamar a ferramenta login, o valor desta vari\u00e1vel de ambiente foi inserido sem verifica\u00e7\u00e3o adicional e sem escapar de caracteres especiais. Portanto, para se conectar como usu\u00e1rio root, basta definir a vari\u00e1vel de ambiente USER como \"-f root\" e conectar ao servidor telnet, especificando a op\u00e7\u00e3o \"-a\": $ USER='-f root' telnet -a nome_do_servidor <\/p>\n

A mudan\u00e7a que levou \u00e0 vulnerabilidade foi introduzida no c\u00f3digo do telnetd em mar\u00e7o de 2015 e estava relacionada \u00e0 corre\u00e7\u00e3o de um problema que impedia a determina\u00e7\u00e3o do nome do usu\u00e1rio em modo autologin sem autentica\u00e7\u00e3o Kerberos. Como solu\u00e7\u00e3o, foi adicionada a capacidade de passar o nome do usu\u00e1rio para o modo autologin atrav\u00e9s de uma vari\u00e1vel de ambiente, mas se esqueceram de adicionar a verifica\u00e7\u00e3o de validade do nome do usu\u00e1rio da vari\u00e1vel de 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. 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usu\u00e1rio, incluindo o usu\u00e1rio root, sem verifica\u00e7\u00e3o de senha.","canonical_url":"https:\/\/prohoster.info\/pt\/blog\/news\/uyazvimost-v-telnetd-pozvolyayushhaya-podklyuchitsya-s-pravami-root-bez-autentifikaczii","robots":"max-image-preview:large","keywords":"","webmasterTools":{"miscellaneous":""},"schema":null,"og:locale":"pt_PT","og:site_name":"ProHoster | \u041a\u0443\u043f\u0438\u0442\u044c \u043d\u0430\u0434\u0435\u0436\u043d\u044b\u0439 \u0445\u043e\u0441\u0442\u0438\u043d\u0433 \u0434\u043b\u044f \u0441\u0430\u0439\u0442\u043e\u0432 \u0441 \u0437\u0430\u0449\u0438\u0442\u043e\u0439 \u043e\u0442 DDoS, VPS VDS \u0441\u0435\u0440\u0432\u0435\u0440\u044b","og:type":"article","og:title":"\ud83e\udd47\u0423\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c \u0432 telnetd, \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u044e\u0449\u0430\u044f \u043f\u043e\u0434\u043a\u043b\u044e\u0447\u0438\u0442\u044c\u0441\u044f \u0441 \u043f\u0440\u0430\u0432\u0430\u043c\u0438 root 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