Segue la vulnerabilit\u00e0 identificata alla fine di gennaio, che consentiva di connettersi come utente root senza verifica della password; nel server telnetd della suite GNU InetUtils sono stati rilevati diversi modi per elevare i propri privilegi, derivanti da una corretta rimozione della vulnerabilit\u00e0 nel 1999 (CVE-1999-0073). <\/p>\n
Le vulnerabilit\u00e0 sono causate dalla possibilit\u00e0 di telnetd di trasmettere variabili d'ambiente dal client al server tramite l'opzione ENVIRON. Tali variabili d'ambiente vengono impostate e trattate nel contesto del processo telnetd e trasmesse ai processi figli avviati, compreso il processo \/bin\/login che viene eseguito con privilegi di root. La vulnerabilit\u00e0 CVE-1999-0073 consentiva al client telnet di trasmettere la variabile d'ambiente LD_LIBRARY_PATH, il cui valore porta al caricamento della libreria condivisa specificata dall'utente durante l'avvio del processo di login. Se il caricamento di file nel sistema supportato dal protocollo telnet \u00e8 possibile, l'attaccante pu\u00f2 caricare una libreria appositamente costruita e organizzare il suo caricamento con privilegi di root. <\/p>\n
In telnetd from the GNU InetUtils set, the vulnerability was addressed by banning dangerous environment variables through filtering masks 'LD_', 'LIBPATH', 'ENV', 'IFS', and '_RLD_'. The 'CREDENTIALS_DIRECTORY' environment variable, however, remained unblocked and is processed during the launch of \/usr\/bin\/login. This environment variable allowed users to change the directory for credential settings and place a login.noauth file with the value 'yes' in the new directory, which activates passwordless login (similar to passing the '-f' flag to the login process). This configuration applies to all users, including root. <\/p>\n
The attack involves a non-privileged user creating a subdirectory in their home directory, uploading the login.noauth file into it, and attempting to log in with the 'CREDENTIALS_DIRECTORY=created_directory' environment variable set, along with passing the 'USER=root' environment variable (telnet has an automatic connection mode where the username is taken not from the command line but passed through the USER environment variable). Here\u2019s an example of the exploit. <\/p>\n
\u00c8 stato identificato un ulteriore metodo per ottenere accesso root tramite telnetd, che riguarda la manipolazione delle variabili d'ambiente OUTPUT_CHARSET e LANGUAGE, gestite dalla libreria GNU gettext, e della variabile d'ambiente GCONV_PATH, utilizzata in glibc. Attraverso l'impostazione delle variabili d'ambiente OUTPUT_CHARSET e LANGUAGE, l'attaccante pu\u00f2 attivare in gettext la funzionalit\u00e0 di conversione della codifica dei caratteri, che richiama la funzione iconv_open(). A sua volta, quando viene eseguita la funzione iconv_open() durante il caricamento del file di configurazione gconv-modules, il percorso viene calcolato tenendo conto della variabile d'ambiente GCONV_PATH. Attraverso la sostituzione del file gconv-modules \u00e8 possibile organizzare il caricamento di una propria libreria condivisa durante l'output di una stringa localizzata dal processo di login. <\/p>\n
CVE identifiers for the noted vulnerabilities have not yet been assigned. A proposed method of protection involves implementing a whitelist of acceptable values ('TERM', 'DISPLAY', 'USER', 'LOGNAME', and 'POSIXLY_CORRECT') while blocking all other environment variables, similar to how environment variables are handled in OpenSSH. The vulnerabilities have been confirmed in the GNU InetUtils package. server<\/a> telnetd \u00e8 fornita in Debian, Ubuntu e distribuzioni derivate. Le correzioni per GNU InetUtils non sono ancora disponibili. In Rocky Linux 9 \u00e8 fornito un telnetd modificato non vulnerabile, nel quale \u00e8 stata implementata un controllo basato su un elenco bianco invece della filtrazione delle variabili d'ambiente pericolose. Anche la filtrazione tramite elenco bianco \u00e8 implementata nel telnetd di FreeBSD. In OpenBSD, telnetd \u00e8 stato rimosso dal sistema nel 2005. \u0421\u043b\u0435\u0434\u043e\u043c \u0437\u0430 \u0432\u044b\u044f\u0432\u043b\u0435\u043d\u043d\u043e\u0439 \u0432 \u043a\u043e\u043d\u0446\u0435 \u044f\u043d\u0432\u0430\u0440\u044f \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c\u044e, \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u0432\u0448\u0435\u0439 \u043f\u043e\u0434\u043a\u043b\u044e\u0447\u0438\u0442\u044c\u0441\u044f \u043f\u043e\u0434 \u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u0442\u0435\u043b\u0435\u043c root \u0431\u0435\u0437 \u043f\u0440\u043e\u0432\u0435\u0440\u043a\u0438 \u043f\u0430\u0440\u043e\u043b\u044f, \u0432 \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\u043e \u043d\u0435\u0441\u043a\u043e\u043b\u044c\u043a\u043e \u0441\u043f\u043e\u0441\u043e\u0431\u043e\u0432 \u043f\u043e\u0432\u044b\u0448\u0435\u043d\u0438\u044f \u0441\u0432\u043e\u0438\u0445 \u043f\u0440\u0438\u0432\u0438\u043b\u0435\u0433\u0438\u0439, \u0441\u0442\u0430\u0432\u0448\u0438\u0445 \u0441\u043b\u0435\u0434\u0441\u0442\u0432\u0438\u0435\u043c \u043d\u0435\u043f\u043e\u043b\u043d\u043e\u0433\u043e \u0443\u0441\u0442\u0440\u0430\u043d\u0435\u043d\u0438\u044f \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0438 \u0432 1999 \u0433\u043e\u0434\u0443 (CVE-1999-0073). \u0423\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0438 \u0432\u044b\u0437\u0432\u0430\u043d\u044b \u043d\u0430\u043b\u0438\u0447\u0438\u0435\u043c \u0432 telnetd \u0432\u043e\u0437\u043c\u043e\u0436\u043d\u043e\u0441\u0442\u0438 \u043f\u0435\u0440\u0435\u0434\u0430\u0447\u0438 \u043a\u043b\u0438\u0435\u043d\u0442\u043e\u043c \u043f\u0435\u0440\u0435\u043c\u0435\u043d\u043d\u044b\u0445 \u043e\u043a\u0440\u0443\u0436\u0435\u043d\u0438\u044f \u043d\u0430 \u0441\u0435\u0440\u0432\u0435\u0440 \u043f\u0440\u0438 \u043f\u043e\u043c\u043e\u0449\u0438 \u043e\u043f\u0446\u0438\u0438 ENVIRON. \u041f\u043e\u0434\u043e\u0431\u043d\u044b\u0435 \u043f\u0435\u0440\u0435\u043c\u0435\u043d\u043d\u044b\u0435 […]<\/p>\n","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"author":8,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[702],"tags":[],"class_list":["post-162791","post","type-post","status-publish","format-standard","hentry","category-news"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\n","aioseo_head_json":{"title":"\ud83e\udd47Una serie di nuove vulnerabilit\u00e0 in telnetd, che consentono di ottenere privilegi root nel sistema | ProHoster","description":"Dopo la vulnerabilit\u00e0 identificata alla fine di gennaio, che consentiva di connettersi come utente root senza verifica della password, nel 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Fonte: opennet.ru<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"