El\u00e9rhet\u0151 egy jav\u00edt\u00f3 kiad\u00e1s az OpenSSH 9.9p2-h\u00f6z, amelyben k\u00e9t, a Qualys \u00e1ltal felfedezett sebezhet\u0151s\u00e9get orvosoltak. Bemutat\u00e1sra ker\u00fclt az eml\u00edtett sebezhet\u0151s\u00e9gek kihaszn\u00e1l\u00e1s\u00e1ra egy p\u00e9lda, amely lehet\u0151v\u00e9 teszi a MITM-t\u00e1mad\u00e1st, amely sor\u00e1n a klient SSH-szerverhez val\u00f3 csatlakoz\u00e1sa sor\u00e1n a forgalmat \u00e1t lehet ir\u00e1ny\u00edtani egy hamis szerverhez, megker\u00fclve a hosztkulcsok ellen\u0151rz\u00e9s\u00e9t, \u00e9s a kliens sz\u00e1m\u00e1ra a k\u00edv\u00e1nt szerverhez val\u00f3 csatlakoz\u00e1s l\u00e1tszat\u00e1t keltve (az ssh-kliens a hamis szerver hosztkulcs\u00e1t fogadja el a legitim szerver kulcsa helyett). <\/p>\n
Az els\u0151 sebezhet\u0151s\u00e9g (CVE-2025-26465) egy logikai hiba miatt k\u00f6vetkezik be az ssh seg\u00e9dprogramban, amely lehet\u0151v\u00e9 teszi a szerverazonos\u00edt\u00e1s megker\u00fcl\u00e9s\u00e9t \u00e9s a MITM-t\u00e1mad\u00e1s v\u00e9grehajt\u00e1s\u00e1t. A probl\u00e9ma az OpenSSH 6.8p1 (2014 december) megjelen\u00e9s\u00e9vel kezd\u0151dik, a VerifyHostKeyDNS be\u00e1ll\u00edt\u00e1ssal rendelkez\u0151 konfigur\u00e1ci\u00f3kban. Az OpenSSH alap\u00e9rtelmezett telep\u00edt\u00e9se eset\u00e9n ez az opci\u00f3 alap\u00e9rtelmezetten ki van kapcsolva, de 2023 m\u00e1rcius\u00e1ig a ssh be\u00e1ll\u00edt\u00e1saiban a FreeBSD-ben enged\u00e9lyezve volt. <\/p>\n
A probl\u00e9ma l\u00e9nyege, hogy a verify_host_key_callback() f\u00fcggv\u00e9ny k\u00f3dj\u00e1ban a verify_host_key() f\u00fcggv\u00e9ny h\u00edv\u00e1sakor csak a «-1» hiba k\u00f3dot ellen\u0151rzik, a «-2» egy\u00e9b k\u00f3dokat pedig figyelmen k\u00edv\u00fcl hagyj\u00e1k. Ennek k\u00f6vetkezt\u00e9ben a verify_host_key_callback() f\u00fcggv\u00e9ny sikeres k\u00f3dot «0» adhat vissza, annak ellen\u00e9re, hogy a verify_host_key() f\u00fcggv\u00e9ny «-2» hib\u00e1t ad vissza. A «-2» hibak\u00f3dot a verify_host_key() f\u00fcggv\u00e9ny adja vissza mem\u00f3riahi\u00e1ny eset\u00e9n. Ha olyan felt\u00e9teleket hozunk l\u00e9tre, amelyek megakad\u00e1lyozz\u00e1k a mem\u00f3ria lefoglal\u00e1s\u00e1t a verify_host_key() f\u00fcggv\u00e9nyben, az SSH azt fogja hinni, hogy a hosztn\u00e9v kulcs\u00e1t sikeresen ellen\u0151rizt\u00e9k. Az ilyen k\u00f6r\u00fclm\u00e9nyek l\u00e9trehoz\u00e1s\u00e1hoz a t\u00e1mad\u00f3 hamis SSH szervere, amelyre az \u00fcgyf\u00e9l \u00e1tir\u00e1ny\u00edt\u00e1sra ker\u00fcl, a lehet\u0151 legnagyobb m\u00e9ret\u0171 hosztn\u00e9v kulcsot (256KB) adja vissza, mik\u00f6zben a ssh kliens oldal\u00e1n mem\u00f3ria sziv\u00e1rg\u00e1st is kiakn\u00e1z. <\/p>\n
A mem\u00f3ria sziv\u00e1rg\u00e1s l\u00e9trehoz\u00e1s\u00e1nak felt\u00e9telei a m\u00e1sodik sebezhet\u0151s\u00e9g (CVE-2025-26466) r\u00e9v\u00e9n val\u00f3sulnak meg, amely mind a ssh klienst, mind a szerver<\/a> sshd, \u00e9s a hiteles\u00edt\u00e9s n\u00e9lk\u00fcli t\u00e1madhat\u00f3s\u00e1g. A sebezhet\u0151s\u00e9g lehet\u0151v\u00e9 teszi a folyamat mem\u00f3ria-kapacit\u00e1s\u00e1nak kimer\u00edt\u00e9s\u00e9t \u00e9s a CPU magas terhel\u00e9s\u00e9nek l\u00e9trehoz\u00e1s\u00e1t a SSH2_MSG_PING csomagok nagy sz\u00e1m\u00fa k\u00fcld\u00e9s\u00e9vel. Az SSH2_MSG_PING csomagok kezel\u0151j\u00e9ben mem\u00f3ria-kisziv\u00e1rg\u00e1s tal\u00e1lhat\u00f3, amely az OpenSSH 9.5p1 (2023 augusztus) kiad\u00e1sa \u00f3ta \u00e9szlelhet\u0151. A sziv\u00e1rg\u00e1s azzal f\u00fcgg \u00f6ssze, hogy minden be\u00e9rkez\u0151 16 byte-os PING csomaghoz 256 byte-os puffert foglalnak le a v\u00e1lasz el\u0151\u00e1ll\u00edt\u00e1s\u00e1ra, de ezt a puffert csak a kulcskonfigur\u00e1ci\u00f3 befejez\u00e9se ut\u00e1n szabad\u00edtj\u00e1k fel. V\u00e9dekez\u00e9sk\u00e9nt a LoginGraceTime, MaxStartups \u00e9s PerSourcePenalties direkt\u00edv\u00e1k be\u00e1ll\u00edt\u00e1s\u00e1val javasolt korl\u00e1toz\u00e1sok alkalmaz\u00e1sa. \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 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Forr\u00e1s: opennet.ru<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"