\u00c8 disponibile un rilascio correttivo di OpenSSH 9.9p2, che risolve due vulnerabilit\u00e0 scoperte da Qualys. \u00c8 stata dimostrata una dimostrazione dell'utilizzo di queste vulnerabilit\u00e0 per eseguire un attacco MITM, consentendo di reindirizzare il traffico su un server fasullo quando un client tenta di connettersi a un server SSH, eludendo il controllo delle chiavi host e dando al client l'apparenza di essere connesso al server desiderato (il client SSH accetter\u00e0 la chiave host del server fasullo al posto di quella del server legittimo). <\/p>\n
La prima vulnerabilit\u00e0 (CVE-2025-26465) \u00e8 causata da un errore logico nell'utilit\u00e0 ssh, che consente di eludere il controllo dell'identificazione del server e di eseguire un attacco MITM. Il problema si manifesta a partire dal rilascio di OpenSSH 6.8p1 (dicembre 2014) in configurazioni con l'impostazione VerifyHostKeyDNS abilitata. Nella distribuzione base di OpenSSH, questa opzione \u00e8 disabilitata per impostazione predefinita, ma \u00e8 stata abilitata nelle impostazioni di ssh su FreeBSD fino a marzo 2023. <\/p>\n
Il problema \u00e8 che nel codice della funzione verify_host_key_callback() quando viene chiamata la funzione verify_host_key() viene controllato solo il codice di errore «-1», mentre altri codici, come «-2», vengono ignorati. Di conseguenza, la funzione verify_host_key_callback() pu\u00f2 restituire un codice di successo «0», nonostante il ritorno dell'errore «-2» dalla funzione verify_host_key(). Il codice di errore «-2» viene restituito dalla funzione verify_host_key() in caso di mancanza di memoria. Se si creano condizioni che portano all'impossibilit\u00e0 di allocare memoria nella funzione verify_host_key(), SSH considerer\u00e0 che la chiave host \u00e8 stata verificata con successo. Per creare tali condizioni, un server SSH fasullo dell'attaccante, a cui il client \u00e8 reindirizzato, restituisce la chiave host di dimensioni massime (256KB) e nello stesso tempo si sfrutta una perdita di memoria sul lato del client SSH. <\/p>\n
Le condizioni per creare una perdita di memoria sono raggiunte grazie a una seconda vulnerabilit\u00e0 (CVE-2025-26466), che colpisce sia il client SSH che il un server<\/a> sshd, e sfruttato senza autenticazione. La vulnerabilit\u00e0 consente di esaurire la memoria disponibile per il processo e di generare un elevato carico sulla CPU inviando un gran numero di pacchetti SSH2_MSG_PING. Nel gestore dei pacchetti SSH2_MSG_PING \u00e8 presente una perdita di memoria, che si manifesta a partire dalla versione OpenSSH 9.5p1 (agosto 2023). La perdita si verifica perch\u00e9 per ogni pacchetto PING di 16 byte viene allocato un buffer di 256 byte per la formazione della risposta, ma questo buffer viene liberato solo dopo il completamento della negoziazione delle chiavi. Come soluzione per la protezione, si consiglia di configurare dei limiti tramite le direttive LoginGraceTime, MaxStartups e PerSourcePenalties. \u0414\u043e\u0441\u0442\u0443\u043f\u0435\u043d \u043a\u043e\u0440\u0440\u0435\u043a\u0442\u0438\u0440\u0443\u044e\u0449\u0438\u0439 \u0432\u044b\u043f\u0443\u0441\u043a OpenSSH 9.9p2, \u0432 \u043a\u043e\u0442\u043e\u0440\u043e\u043c \u0443\u0441\u0442\u0440\u0430\u043d\u0435\u043d\u044b \u0434\u0432\u0435 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0438, \u0432\u044b\u044f\u0432\u043b\u0435\u043d\u043d\u044b\u0435 \u043a\u043e\u043c\u043f\u0430\u043d\u0438\u0435\u0439 Qualys. \u041f\u0440\u043e\u0434\u0435\u043c\u043e\u043d\u0441\u0442\u0440\u0438\u0440\u043e\u0432\u0430\u043d \u043f\u0440\u0438\u043c\u0435\u0440 \u0438\u0441\u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u043d\u0438\u044f \u0434\u0430\u043d\u043d\u044b\u0445 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0435\u0439 \u0434\u043b\u044f \u0441\u043e\u0432\u0435\u0440\u0448\u0435\u043d\u0438\u044f MITM-\u0430\u0442\u0430\u043a\u0438, \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u044e\u0449\u0435\u0439 \u043f\u0440\u0438 \u043f\u043e\u043f\u044b\u0442\u043a\u0435 \u043f\u043e\u0434\u043a\u043b\u044e\u0447\u0435\u043d\u0438\u044f \u043a\u043b\u0438\u0435\u043d\u0442\u0430 \u043a SSH-\u0441\u0435\u0440\u0432\u0435\u0440\u0443, \u043f\u0435\u0440\u0435\u043d\u0430\u043f\u0440\u0430\u0432\u0438\u0442\u044c \u0442\u0440\u0430\u0444\u0438\u043a \u043d\u0430 \u0441\u043e\u0431\u0441\u0442\u0432\u0435\u043d\u043d\u044b\u0439 \u0444\u0438\u043a\u0442\u0438\u0432\u043d\u044b\u0439 \u0441\u0435\u0440\u0432\u0435\u0440, \u043e\u0431\u043e\u0439\u0442\u0438 \u043f\u0440\u043e\u0432\u0435\u0440\u043a\u0443 \u0445\u043e\u0441\u0442\u043e\u0432\u044b\u0445 \u043a\u043b\u044e\u0447\u0435\u0439 \u0438 \u0441\u043e\u0437\u0434\u0430\u0442\u044c \u0443 \u043a\u043b\u0438\u0435\u043d\u0442\u0430 \u0432\u0438\u0434\u0438\u043c\u043e\u0441\u0442\u044c \u043f\u043e\u0434\u043a\u043b\u044e\u0447\u0435\u043d\u0438\u044f \u043a \u0436\u0435\u043b\u0430\u0435\u043c\u043e\u043c\u0443 \u0441\u0435\u0440\u0432\u0435\u0440\u0443 (ssh-\u043a\u043b\u0438\u0435\u043d\u0442 \u043f\u0440\u0438\u043c\u0435\u0442 \u0445\u043e\u0441\u0442\u043e\u0432\u044b\u0439 \u043a\u043b\u044e\u0447 \u0444\u0438\u043a\u0442\u0438\u0432\u043d\u043e\u0433\u043e \u0441\u0435\u0440\u0432\u0435\u0440\u0430 \u0432\u043c\u0435\u0441\u0442\u043e \u043a\u043b\u044e\u0447\u0430 […]<\/p>\n","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[702],"tags":[],"class_list":["post-121998","post","type-post","status-publish","format-standard","hentry","category-novosti-interneta"],"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\udd47Aggiornamento OpenSSH 9.9p2 con correzione della vulnerabilit\u00e0 MITM | ProHoster","description":"\u00c8 disponibile un aggiornamento corretto per OpenSSH 9.9p2, che risolve due vulnerabilit\u00e0 scoperte da Qualys. \u00c8 stato dimostrato un esempio di sfruttamento di queste vulnerabilit\u00e0 per eseguire un attacco MITM, consentendo di reindirizzare il traffico verso un server fasullo al momento della connessione del client al server SSH, eludendo la verifica delle chiavi host e creando l'apparenza per il client di essere connesso al server desiderato (il client SSH accetter\u00e0 la chiave host del server fasullo invece di quella originale)","canonical_url":"https:\/\/prohoster.info\/it\/blog\/novosti-interneta\/obnovlenie-openssh-9-9p2-s-ustraneniem-vozmozhnosti-soversheniya-mitm-ataki","robots":"max-image-preview:large","keywords":"","webmasterTools":{"miscellaneous":""},"schema":null,"og:locale":"it_IT","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\u041e\u0431\u043d\u043e\u0432\u043b\u0435\u043d\u0438\u0435 OpenSSH 9.9p2 \u0441 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Fonte: opennet.ru<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"