{"id":172668,"date":"2026-05-19T06:24:52","date_gmt":"2026-05-19T04:24:52","guid":{"rendered":"https:\/\/prohoster.info\/blog\/novosti-interneta\/v-linux-zakryta-uyazvimost-ssh-keysign-pwn-pozvolyayushhaya-lokalnym-polzovatelyam-chitat-root-fajly"},"modified":"2026-05-19T12:52:18","modified_gmt":"2026-05-19T10:52:18","slug":"v-linux-zakryta-uyazvimost-ssh-keysign-pwn-pozvolyayushhaya-lokalnym-polzovatelyam-chitat-root-fajly","status":"publish","type":"post","link":"https:\/\/prohoster.info\/sl\/blog\/news\/v-linux-zakryta-uyazvimost-ssh-keysign-pwn-pozvolyayushhaya-lokalnym-polzovatelyam-chitat-root-fajly","title":{"rendered":"V Linuxu je bila zaprta ranljivost ssh-keysign-pwn, ki omogo\u010da lokalnim uporabnikom branje root-datotek.","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"<p>V jedru Linux je bila odpravljena ranljivost, ki je dobila neuradno ime <strong>ssh-keysign-pwn<\/strong>. Te\u017eava omogo\u010da lokalnemu nevzpostavljenemu uporabniku branje datotek, ki bi morale biti dostopne samo rootu, vklju\u010dno s zasebnimi SSH host-klju\u010di in v dolo\u010denih scenarijih tudi \/etc\/shadow. Ob objavi \u0161e ni bila dodeljena lo\u010dena CVE za to te\u017eavo.<\/p>\n<p>  <noindex><noindex><\/p>\n<p>Kljub imenu te\u017eava ni napaka v OpenSSH kot omre\u017eni stre\u017enik sshd, temve\u010d gre za <a rel=\"nofollow\" href=\"https:\/\/github.com\/torvalds\/linux\/commit\/31e62c2ebbfdc3fe3dbdf5e02c92a9dc67087a3a\">defekt<\/a> v logiki jedra Linux, povezane s preverjanjem ptrace in dostopom do datote\u010dnih descriptorjev drugega procesa preko pidfd_getfd(2). Orodje OpenSSH ssh-keysign se je izkazalo za enega izmed priro\u010dnih primerov izkori\u0161\u010danja, ker dela z zasebnimi host-klju\u010di, ki obi\u010dajno pripadajo rootu in niso dostopni obi\u010dajnim uporabnikom.<\/p>\n<p><\/noindex><\/noindex> <noindex><\/p>\n<p><a rel=\"nofollow\" href=\"https:\/\/github.com\/0xdeadbeefnetwork\/ssh-keysign-pwn\">Jedro napake<\/a> je v tem, da funkcija __ptrace_may_access() neustrezno obravnava stanje procesa, pri katerem je \u017ee izginila struktura pomnilnika mm, a so \u0161e odprti datote\u010dni deskriptorji. Med koncem procesa jedro pokli\u010de exit_mm() prej, kot zapre datoteke preko exit_files(). V tem kratkem intervalu se proces \u017ee zdi, da nima obi\u010dajnega uporabni\u0161kega naslovnega prostora, a njegovi odprti datoteki \u0161e vedno obstajajo. Zaradi tega bi se lahko pre\u0161la kontrola stanja \u201edumpable\u201c, medtem pa bi pidfd_getfd() dobil dostop do tujega datote\u010dnega deskriptorja ob ujemajo\u010dem UID.<\/p>\n<p><\/noindex> <\/p>\n<p>Prakti\u010den scenarij temelji na setuid programih, ki najprej odprejo ob\u010dutljivo datoteko s pravicami root, nato pa privilegije prekli\u010dejo in kon\u010dajo, \u0161e vedno obdr\u017eijo odprti deskriptor. V objavljenem opisu je kot primer naveden ssh-keysign: odpre \/etc\/ssh\/ssh_host_{ecdsa,ed25519,rsa}_key, nato pa prekli\u010de pravice in se lahko kon\u010da, \u010de je EnableSSHKeysign onemogo\u010den. Ti klju\u010di bi morali biti dostopni le rootu, ker se uporabljajo za avtentikacijo na osnovi host.<\/p>\n<p>Drugi primer je chage, ki lahko odpre \/etc\/shadow, nato pa prekli\u010de u\u010dinkovite pravice in se kon\u010da. Posledi\u010dno napad ne prina\u0161a takoj shell z root pravicami, ampak omogo\u010da dostop do vsebine datotek, ki se obi\u010dajno \u0161tejejo za kriti\u010dne. Izlivanje \/etc\/shadow predstavlja nevarnost zaradi mo\u017enosti kasnej\u0161ega offline oblikovanja gesel, medtem ko izlivanje zasebnih SSH host-klju\u010dev predstavlja tveganje zamenjave gostitelja ali izvajanja napadov na zaupanja vredne SSH scenarije.<\/p>\n<p>\u0418\u0441\u043f\u0440\u0430\u0432\u043b\u0435\u043d\u0438\u0435 \u0443\u0436\u0435 \u043f\u0440\u0438\u043d\u044f\u0442\u043e \u0432 \u043e\u0441\u043d\u043e\u0432\u043d\u0443\u044e \u0432\u0435\u0442\u043a\u0443 Linux. \u041a\u043e\u043c\u043c\u0438\u0442 31e62c2ebbfd \u0441 \u0437\u0430\u0433\u043e\u043b\u043e\u0432\u043a\u043e\u043c ptrace: slightly saner &#8216;get_dumpable()&#8217; logic \u043c\u0435\u043d\u044f\u0435\u0442 \u043f\u043e\u0432\u0435\u0434\u0435\u043d\u0438\u0435 \u043f\u0440\u043e\u0432\u0435\u0440\u043a\u0438 dumpability: \u044f\u0434\u0440\u043e \u0442\u0435\u043f\u0435\u0440\u044c \u0441\u043e\u0445\u0440\u0430\u043d\u044f\u0435\u0442 \u0441\u043e\u0441\u0442\u043e\u044f\u043d\u0438\u0435 user_dumpable \u043f\u0440\u0438 \u0438\u0441\u0447\u0435\u0437\u043d\u043e\u0432\u0435\u043d\u0438\u0438 mm \u0438 \u0442\u0440\u0435\u0431\u0443\u0435\u0442 \u043a\u043e\u0440\u0440\u0435\u043a\u0442\u043d\u0443\u044e \u043f\u0440\u043e\u0432\u0435\u0440\u043a\u0443 CAP_SYS_PTRACE \u0434\u043b\u044f \u043e\u0431\u0445\u043e\u0434\u0430. \u041f\u0430\u0442\u0447 \u0437\u0430\u0442\u0440\u0430\u0433\u0438\u0432\u0430\u0435\u0442 include\/linux\/sched.h, kernel\/exit.c \u0438 kernel\/ptrace.c.<\/p>\n<p>Vulnerabilnost je prijavljena od strane Qualys-a i ispravio ju je Linus Torvalds 14. maja 2026. godine. Phoronix napominje da je u trenutku objavljivanja problem poga\u0111ao sve verzije Linux jezgra do trenutnog stanja mainline grane pre ispravke. Autor PoC tako\u0111e ukazuje da su ranjivi i kernel-i pre commita 31e62c2ebbfd, uklju\u010duju\u0107i stabilne grane zaklju\u010dno sa 14. majem.<\/p>\n<p> <noindex><\/p>\n<p>Odvojeno je va\u017eno da za eksploataciju nije potrebno u\u010ditavati specifi\u010dne module jezgra, kao u slu\u010daju brojnih nedavnih LPE ranjivosti. Dovoljno je lokalno neprivilegovano pristupiti sistemu i imati odgovaraju\u0107i privilegovani helper-proces. Razvija\u010d Debiana Daniel Baumann <a rel=\"nofollow\" href=\"https:\/\/blog.daniel-baumann.ch\/posts\/20260515-1.html\">primetio<\/a>, da bi ovaj problem trebalo re\u0161iti a\u017euriranjem jezgra i naknadnim restartovanjem na ispravno jezgro.<\/p>\n<p><\/noindex> <\/p>\n<p>U objavljenom repozitorijumu sa demonstracijom navedena je provera na Raspberry Pi OS Bookworm sa jezgrom 6.12.75, Debian 13, Ubuntu 22.04, Ubuntu 24.04, Ubuntu 26.04, Arch i CentOS 9. Ovu listu treba smatrati kao podatke autora PoC, a ne kao sveobuhvatan spisak: budu\u0107i da se gre\u0161ka nalazi u op\u0161toj logici jezgra, stvarni obuhvat zavisi od verzije jezgra i postojanja backport- ispravke kod odre\u0111enog distribucije.<\/p>\n<p>Za administratore je osnovna preporuka jednostavna: instalirati a\u017eurirani paket jezgra od svog distribucije i restartovati sistem. Ako postoje osnovi za sumnju da je na ma\u0161ini ve\u0107 bio lokalni neprivilegovani pristup napada\u010da, nakon a\u017euriranja treba dodatno razmotriti rotaciju SSH host-klju\u010deva i proveru \/etc\/shadow\/ korisni\u010dkih ra\u010duna, budu\u0107i da je sama ranjivost povezana upravo sa \u010ditanjem osetljivih datoteka, a ne samo sa apstraktnim zaobila\u017eenjem provere pristupa.<\/p>\n<p>U Debiana je ve\u0107 po\u010dela izrada prevoda ispravke: Baumann je izvestio o cherry-pick upstream commit-a u trixie-fastforward-backports i o slanju merge request-a za Debian sid. U merge request-u je jasno nazna\u010deno da se prenosi commit 31e62c2 za ispravku ptrace logike dumpability, koja omogu\u0107ava neprivilegovanom korisniku da \u010dita root datoteke.<\/p>\n<p>Izvor: <a \ncontent=\"nofollow\" rel=\"nofollow\" href=\"https:\/\/www.linux.org.ru\/news\/security\/18293396\">linux.org.ru<\/a><\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"<p>\u0412 \u044f\u0434\u0440\u0435 Linux \u0438\u0441\u043f\u0440\u0430\u0432\u043b\u0435\u043d\u0430 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c, \u043f\u043e\u043b\u0443\u0447\u0438\u0432\u0448\u0430\u044f \u043d\u0435\u043e\u0444\u0438\u0446\u0438\u0430\u043b\u044c\u043d\u043e\u0435 \u043d\u0430\u0437\u0432\u0430\u043d\u0438\u0435 ssh-keysign-pwn. \u041f\u0440\u043e\u0431\u043b\u0435\u043c\u0430 \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u0435\u0442 \u043b\u043e\u043a\u0430\u043b\u044c\u043d\u043e\u043c\u0443 \u043d\u0435\u043f\u0440\u0438\u0432\u0438\u043b\u0435\u0433\u0438\u0440\u043e\u0432\u0430\u043d\u043d\u043e\u043c\u0443 \u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u0442\u0435\u043b\u044e \u0447\u0438\u0442\u0430\u0442\u044c \u0444\u0430\u0439\u043b\u044b, \u043a\u043e\u0442\u043e\u0440\u044b\u0435 \u0434\u043e\u043b\u0436\u043d\u044b \u0431\u044b\u0442\u044c \u0434\u043e\u0441\u0442\u0443\u043f\u043d\u044b \u0442\u043e\u043b\u044c\u043a\u043e root, \u0432\u043a\u043b\u044e\u0447\u0430\u044f \u043f\u0440\u0438\u0432\u0430\u0442\u043d\u044b\u0435 SSH host-\u043a\u043b\u044e\u0447\u0438 \u0438, \u0432 \u043e\u0442\u0434\u0435\u043b\u044c\u043d\u044b\u0445 \u0441\u0446\u0435\u043d\u0430\u0440\u0438\u044f\u0445, \/etc\/shadow. \u041d\u0430 \u043c\u043e\u043c\u0435\u043d\u0442 \u043f\u0443\u0431\u043b\u0438\u043a\u0430\u0446\u0438\u0438 \u043e\u0442\u0434\u0435\u043b\u044c\u043d\u044b\u0439 CVE \u0434\u043b\u044f \u043f\u0440\u043e\u0431\u043b\u0435\u043c\u044b \u0435\u0449\u0451 \u043d\u0435 \u0431\u044b\u043b \u043d\u0430\u0437\u043d\u0430\u0447\u0435\u043d. \u041d\u0435\u0441\u043c\u043e\u0442\u0440\u044f \u043d\u0430 \u043d\u0430\u0437\u0432\u0430\u043d\u0438\u0435, \u0440\u0435\u0447\u044c \u0438\u0434\u0451\u0442 \u043d\u0435 \u043e\u0431 \u043e\u0448\u0438\u0431\u043a\u0435 \u0432 OpenSSH \u043a\u0430\u043a \u0441\u0435\u0442\u0435\u0432\u043e\u043c \u0441\u0435\u0440\u0432\u0435\u0440\u0435 [&hellip;]<\/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-172668","post","type-post","status-publish","format-standard","hentry","category-news"],"aioseo_notices":[],"aioseo_head":"\n\t\t<!-- All in One SEO 5.0.4 - aioseo.com -->\n\t<meta name=\"description\" content=\"\u0412 \u044f\u0434\u0440\u0435 Linux 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