{"id":162791,"date":"2026-02-25T17:11:54","date_gmt":"2026-02-25T15:11:54","guid":{"rendered":"https:\/\/prohoster.info\/blog\/novosti-interneta\/seriya-novyh-uyazvimostej-v-telnetd-pozvolyayushhih-poluchit-root-privilegii-v-sisteme"},"modified":"2026-02-25T17:11:54","modified_gmt":"2026-02-25T15:11:54","slug":"seriya-novyh-uyazvimostej-v-telnetd-pozvolyayushhih-poluchit-root-privilegii-v-sisteme","status":"publish","type":"post","link":"https:\/\/prohoster.info\/sv\/blog\/news\/seriya-novyh-uyazvimostej-v-telnetd-pozvolyayushhih-poluchit-root-privilegii-v-sisteme","title":{"rendered":"En serie nya s\u00e5rbarheter i telnetd som m\u00f6jligg\u00f6r root-privilegier i systemet","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

I februari uppt\u00e4cktes en s\u00e5rbarhet som till\u00e4t att logga in som root-anv\u00e4ndare utan l\u00f6senordsverifiering. Flera s\u00e4tt att \u00f6ka sina privilegier har nu identifierats i telnetd-servern fr\u00e5n GNU InetUtils, till f\u00f6ljd av en ofullst\u00e4ndig \u00e5tg\u00e4rd av en s\u00e5rbarhet som uppt\u00e4cktes 1999 (CVE-1999-0073). <\/p>\n

S\u00e5rbarheterna orsakas av att telnetd till\u00e5ter att klienten skickar milj\u00f6variabler till servern med hj\u00e4lp av ENVIRON-alternativet. Dessa milj\u00f6variabler hanteras i sammanhanget av telnetd-processen och vidarebefordras till de underprocesser som k\u00f6rs av den, inklusive processen \/bin\/login som k\u00f6rs med root-r\u00e4ttigheter. S\u00e5rbarheten CVE-1999-0073 till\u00e4t telnet-klienten att skicka milj\u00f6variabeln LD_LIBRARY_PATH, vars inst\u00e4llning ledde till att den angivna delade biblioteket laddades vid start av login-processen. Om det finns m\u00f6jlighet att ladda filer till systemet som st\u00f6der telnet-anslutningar kan angriparen ladda ett speciellt utformat bibliotek och organisera dess laddning med root-r\u00e4ttigheter. <\/p>\n

I telnetd fr\u00e5n GNU InetUtils har en s\u00e5rbarhet \u00e5tg\u00e4rdats genom att f\u00f6rbjuda farliga milj\u00f6variabler genom filtrering baserat p\u00e5 m\u00f6nstret «LD_», «LIBPATH», «ENV», «IFS» och «_RLD_». Den ofiltrerade milj\u00f6variabeln «CREDENTIALS_DIRECTORY» p\u00e5verkas dock, vilket hanteras vid starten av \/usr\/bin\/login. Genom denna milj\u00f6variabel kunde en anv\u00e4ndare \u00e4ndra katalogen f\u00f6r autentiseringsinst\u00e4llningar och placera en fil login.noauth med v\u00e4rdet «yes», vilket m\u00f6jligg\u00f6r inloggning utan l\u00f6senord (motsvarar att skicka flaggan «-f» till login-processen). Inst\u00e4llningen p\u00e5verkar alla anv\u00e4ndare, inklusive root. <\/p>\n

Attacken handlar om att en icke-privilegierad anv\u00e4ndare skapar en underkatalog i sin hemkatalog, laddar upp filen login.noauth dit och f\u00f6rs\u00f6ker logga in genom att s\u00e4tta milj\u00f6variabeln «CREDENTIALS_DIRECTORY=skapat katalog» och skicka milj\u00f6variabeln «USER=root» (i telnet finns ett automatiskt anslutningsl\u00e4ge d\u00e4r anv\u00e4ndarnamnet tas inte fr\u00e5n kommandoraden utan skickas via milj\u00f6variabeln USER). Ett exempel p\u00e5 ett exploit. <\/p>\n

Ytterligare ett s\u00e4tt att f\u00e5 root-\u00e5tkomst via telnetd har uppt\u00e4ckts. Detta \u00e4r kopplat till manipulering av milj\u00f6variablerna OUTPUT_CHARSET och LANGUAGE, som hanteras av GNU gettext-biblioteket, samt milj\u00f6variabeln GCONV_PATH, som anv\u00e4nds i glibc. Genom att st\u00e4lla in milj\u00f6variablerna OUTPUT_CHARSET och LANGUAGE kan en angripare aktivera funktionaliteten f\u00f6r teckenkodningskonvertering i gettext, vilket aktiverar funktionen iconv_open(). N\u00e4r funktionen iconv_open() exekveras vid laddning av konfigurationsfilen gconv-modules ber\u00e4knas s\u00f6kv\u00e4gen med h\u00e4nsyn till milj\u00f6variabeln GCONV_PATH. Genom att byta ut gconv-modules-filen kan en angripare orsaka att en egen delad bibliotek laddas vid utskrift av en lokaliserad str\u00e4ng av login-processen. <\/p>\n

CVE-id har \u00e4nnu inte tilldelats de markerade s\u00e5rbarheterna. Som ett skyddsmethod \u00f6verv\u00e4gs att anv\u00e4nda en vit lista \u00f6ver till\u00e5tna v\u00e4rden («TERM», «DISPLAY», «USER», «LOGNAME» och «POSIXLY_CORRECT») med blockering av alla andra milj\u00f6variabler, p\u00e5 samma s\u00e4tt som hantering av milj\u00f6variabler i OpenSSH. S\u00e5rbarheten har bekr\u00e4ftats i GNU InetUtils-paketet, implementering. servern<\/a> I Rocky Linux 9 levereras en modifierad telnetd som inte \u00e4r s\u00e5rbar, d\u00e4r ist\u00e4llet f\u00f6r filtrering av farliga milj\u00f6variabler en vitlistakontroll inkluderas. Filtrering enligt vitlista har ocks\u00e5 genomf\u00f6rts i telnetd fr\u00e5n FreeBSD. I OpenBSD togs telnetd bort fr\u00e5n systemet \u00e5r 2005.
\n
K\u00e4lla: opennet.ru<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

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s\u00e4tt att h\u00f6ja sina privilegier uppt\u00e4ckts i telnetd-servern fr\u00e5n GNU InetUtils.","canonical_url":"https:\/\/prohoster.info\/sv\/blog\/news\/seriya-novyh-uyazvimostej-v-telnetd-pozvolyayushhih-poluchit-root-privilegii-v-sisteme","robots":"max-image-preview:large","keywords":"","webmasterTools":{"miscellaneous":""},"schema":null,"og:locale":"sv_SE","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\u0421\u0435\u0440\u0438\u044f \u043d\u043e\u0432\u044b\u0445 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0435\u0439 \u0432 telnetd, \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u044e\u0449\u0438\u0445 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