{"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\/da\/blog\/news\/uyazvimost-v-telnetd-pozvolyayushhaya-podklyuchitsya-s-pravami-root-bez-autentifikaczii","title":{"rendered":"S\u00e5rbarhed i telnetd, der tillader tilslutning med root-rettigheder uden autentificering","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

Der telnetd-server i GNU InetUtils har en s\u00e5rbarhed, der tillader tilslutning som enhver bruger, inklusive root-brugeren, uden at der bliver tjekket for kodeord. CVE-identifikatoren er endnu ikke tildelt. S\u00e5rbarheden optr\u00e6der fra version InetUtils 1.9.3 (2015) og forbliver uforl\u00f8st i den aktuelle version 2.7.0. En rettelse er tilg\u00e6ngelig i form af patches (1, 2). <\/p>\n

Problemet skyldes, at telnetd-processen til kontrol af adgangskoden kalder programmet «\/usr\/bin\/login», idet den sender brugernavnet, som klienten angav ved tilslutningen, som argument. server<\/a>. Programmet «login» underst\u00f8tter indstillingen «-f», som lader brugeren logge ind uden at gennemg\u00e5 godkendelsestrin (det antages, at denne indstilling bruges, n\u00e5r brugeren allerede er blevet verificeret). S\u00e5ledes, hvis man kan f\u00e5 indstillingen «-f» indsat i brugernavnet, kan man logge ind uden at skulle angive en adgangskode. <\/p>\n

Ved en normal tilslutning vil det ikke v\u00e6re muligt at bruge et brugernavn som «-f root», men telnet har en automatisk tilslutningstilstand, der aktiveres med indstillingen «-a». I denne tilstand hentes brugernavnet ikke fra kommandolinjen, men sendes gennem milj\u00f8variablen USER. N\u00e5r programmet login kaldes, inds\u00e6ttes v\u00e6rdien af denne milj\u00f8variabel uden yderligere kontrol og uden at specialtegn escaperes. For at tilslutte som brugeren root, er det tilstr\u00e6kkeligt at indstille milj\u00f8variablen USER til v\u00e6rdien «-f root» og forbinde til telnetserveren med indstillingen «-a»: $ USER=’-f root’ telnet -a server_navn <\/p>\n

\u00c6ndringen, der for\u00e5rsagede s\u00e5rbarheden, blev tilf\u00f8jet i koden til telnetd i marts 2015 og var relateret til l\u00f8sning af et problem, der ikke tillod identifikation af brugernavnet i autologin-tilstand uden autentificering i Kerberos. For at l\u00f8se dette blev der tilf\u00f8jet underst\u00f8ttelse til at videregive brugernavnet til autologin-tilstand via milj\u00f8variablen, men man glemte at tilf\u00f8je en kontrol af korrektheden af brugernavnet fra milj\u00f8variablen.
\n
Kilde: 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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