{"id":149133,"date":"2025-11-21T17:11:55","date_gmt":"2025-11-21T15:11:55","guid":{"rendered":"https:\/\/prohoster.info\/blog\/novosti-interneta\/6-uyazvimostej-v-zagruzchike-grub2-pozvolyayushhih-obojti-uefi-secure-boot"},"modified":"2025-11-21T17:11:55","modified_gmt":"2025-11-21T15:11:55","slug":"6-uyazvimostej-v-zagruzchike-grub2-pozvolyayushhih-obojti-uefi-secure-boot","status":"publish","type":"post","link":"https:\/\/prohoster.info\/sv\/blog\/news\/6-uyazvimostej-v-zagruzchike-grub2-pozvolyayushhih-obojti-uefi-secure-boot","title":{"rendered":"6 s\u00e5rbarheter i GRUB2-laddaren som g\u00f6r det m\u00f6jligt att kringg\u00e5 UEFI Secure Boot","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"<p>Ett set av patchar har publicerats f\u00f6r att \u00e5tg\u00e4rda 6 s\u00e5rbarheter i GRUB2-bootloadern, varav de flesta leder till access av minnet efter att det har frigjorts (use-after-free). Potentiellt uppt\u00e4ckta problem kan utnyttjas f\u00f6r att kringg\u00e5 mekanismen f\u00f6r verifierad uppstart UEFI Secure Boot. Status f\u00f6r \u00e5tg\u00e4rder av s\u00e5rbarheter i distributioner kan bed\u00f6mas p\u00e5 f\u00f6ljande sidor: Debian, Ubuntu, SUSE, RHEL, Arch och Fedora. F\u00f6r att \u00e5tg\u00e4rda problemen i GRUB2 r\u00e4cker det inte med att bara uppdatera paketet; det \u00e4r ocks\u00e5 n\u00f6dv\u00e4ndigt att skapa nya interna digitala signaturer och uppdatera installationsprogram, bootloaders, k\u00e4rnpaket, fwupd-firmware och shim-lagret.         <\/p>\n<p>Uppt\u00e4ckta s\u00e5rbarheter:  <\/p>\n<ul>\n<li class=\"l\"> CVE-2025-61661 \u2014 \u00f6vertr\u00e4delse av det allokerade bufferns gr\u00e4nser i funktionen grub_usb_get_string(), som kan utnyttjas vid hantering av str\u00e4ngar i UTF-8- och UTF-16-kodningar som skickas vid anslutning av USB-enheter. Problemet orsakas av att buffern allokerades baserat p\u00e5 storleken p\u00e5 str\u00e4ngen som angavs i det f\u00f6rsta meddelandet fr\u00e5n USB-enheten, medan storleken vid kodningstransformeringen ber\u00e4knades baserat p\u00e5 efterf\u00f6ljande l\u00e4soperationer fr\u00e5n USB-enheten. D\u00e4rf\u00f6r kan en modifierad USB-enhet anv\u00e4ndas f\u00f6r attacken, som inledningsvis returnerar ett underskattat v\u00e4rde f\u00f6r storlek.\n<li class=\"l\"> CVE-2025-61663, CVE-2025-61664, CVE-2025-54770, CVE-2025-61662 \u2014 brist p\u00e5 rensning av kommandohanterare 'normal', 'normal_exit', 'net_set_vlan' och 'gettext' vid avlastning av modulerna 'normal', 'net' och 'gettext', vilket skapar f\u00f6ruts\u00e4ttningar f\u00f6r minnes\u00e5tkomst efter att det har frigjorts (use-after-free) om de angivna kommandona utf\u00f6rs efter avlastning av motsvarande moduler. Liknande s\u00e5rbarheter har ocks\u00e5 uppt\u00e4ckts f\u00f6r kommandona 'functional_test' och 'all_functional_test', men de har inte tilldelats CVE-ID, eftersom dessa kommandon ing\u00e5r i testbiblioteket och inte b\u00f6r inkluderas i produktionskompileringar.\n<li class=\"l\"> CVE-2025-54771 \u2014 ett fel vid r\u00e4kning av referenser till 'fs'-strukturer i funktionen grub_file_close(), vilket leder till minnes\u00e5tkomst efter att det har frigjorts (use-after-free).        <\/ul>\n<p>I de flesta Linux-distributioner anv\u00e4nds ett litet lager shim, som \u00e4r certifierat med en digital signatur av Microsoft, f\u00f6r verifierad uppstart i UEFI Secure Boot-l\u00e4ge. Detta lager verifierar GRUB2 med sin egen certifikat, vilket g\u00f6r att distributionsutvecklare inte beh\u00f6ver certifiera varje k\u00e4rn- och GRUB-uppdatering hos Microsoft. S\u00e5rbarheter i GRUB2 kan utnyttjas f\u00f6r att k\u00f6ra kod efter att shim verifierats framg\u00e5ngsrikt, men innan operativsystemet startas, genom att bryta kedjan av f\u00f6rtroende under aktivt Secure Boot-l\u00e4ge och ta full kontroll \u00f6ver den fortsatta startprocessen, exempelvis f\u00f6r att starta ett annat operativsystem, modifiera operativsystemskomponenter och kringg\u00e5 Lockdown-skyddet.     <\/p>\n<p>F\u00f6r att blockera s\u00e5rbarheten utan att \u00e5terkalla den digitala signaturen kan distributioner anv\u00e4nda mekanismen SBAT (UEFI Secure Boot Advanced Targeting), vars st\u00f6d har implementerats f\u00f6r GRUB2, shim och fwupd i de flesta popul\u00e4ra Linux-distributioner. SBAT har utvecklats i samarbete med Microsoft och inneb\u00e4r att ytterligare metadata som inkluderar information om tillverkare, produkt, komponent och version l\u00e4ggs till i exekverbara filer f\u00f6r UEFI. Dessa metadata signeras digitalt och kan separat ing\u00e5 i listor \u00f6ver till\u00e5tna eller f\u00f6rbjudna komponenter f\u00f6r UEFI Secure Boot.      <\/p>\n<p>SBAT g\u00f6r det m\u00f6jligt att blockera anv\u00e4ndningen av digitala signaturer f\u00f6r specifika versionsnummer av komponenter utan att beh\u00f6va \u00e5terkalla nycklar f\u00f6r Secure Boot. Blockering av s\u00e5rbarheter via SBAT kr\u00e4ver inte anv\u00e4ndning av en lista \u00f6ver \u00e5terkallade UEFI-certifikat (dbx), utan sker p\u00e5 niv\u00e5 av att ers\u00e4tta den interna nyckeln f\u00f6r att skapa signaturer och uppdatera GRUB2, shim och andra bootartefakter som levereras med distributioner. Innan SBAT inf\u00f6rdes var det obligatoriskt att uppdatera listan \u00f6ver \u00e5terkallade certifikat (dbx, UEFI Revocation List) f\u00f6r att helt blockera s\u00e5rbarheten, eftersom angriparen, oavsett vilken operativsystem som anv\u00e4nds, kunde utnyttja en startbar enhet med en gammal s\u00e5rbar version av GRUB2 som var certifierad med en digital signatur.<br \/>\n<br \/>K\u00e4lla: <a content=\"nofollow\" rel=\"nofollow\" href=\"https:\/\/www.opennet.ru\/opennews\/art.shtml?num=64298\">opennet.ru<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"<p>\u041e\u043f\u0443\u0431\u043b\u0438\u043a\u043e\u0432\u0430\u043d \u043d\u0430\u0431\u043e\u0440 \u043f\u0430\u0442\u0447\u0435\u0439 \u0441 \u0443\u0441\u0442\u0440\u0430\u043d\u0435\u043d\u0438\u0435\u043c 6 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0435\u0439 \u0432 \u0437\u0430\u0433\u0440\u0443\u0437\u0447\u0438\u043a\u0435 GRUB2, \u0431\u043e\u043b\u044c\u0448\u0438\u043d\u0441\u0442\u0432\u043e \u0438\u0437 \u043a\u043e\u0442\u043e\u0440\u044b\u0445 \u043f\u0440\u0438\u0432\u043e\u0434\u0438\u0442 \u043a \u043e\u0431\u0440\u0430\u0449\u0435\u043d\u0438\u044e \u043a \u043f\u0430\u043c\u044f\u0442\u0438 \u043f\u043e\u0441\u043b\u0435 \u0435\u0451 \u043e\u0441\u0432\u043e\u0431\u043e\u0436\u0434\u0435\u043d\u0438\u044f (use-after-free). \u041f\u043e\u0442\u0435\u043d\u0446\u0438\u0430\u043b\u044c\u043d\u043e \u0432\u044b\u044f\u0432\u043b\u0435\u043d\u043d\u044b\u0435 \u043f\u0440\u043e\u0431\u043b\u0435\u043c\u044b \u043c\u043e\u0433\u0443\u0442 \u0438\u0441\u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u0442\u044c\u0441\u044f \u0434\u043b\u044f \u043e\u0431\u0445\u043e\u0434\u0430 \u043c\u0435\u0445\u0430\u043d\u0438\u0437\u043c\u0430 \u0432\u0435\u0440\u0438\u0444\u0438\u0446\u0438\u0440\u043e\u0432\u0430\u043d\u043d\u043e\u0439 \u0437\u0430\u0433\u0440\u0443\u0437\u043a\u0438 UEFI Secure Boot. \u0421\u0442\u0430\u0442\u0443\u0441 \u0443\u0441\u0442\u0440\u0430\u043d\u0435\u043d\u0438\u044f \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0435\u0439 \u0432 \u0434\u0438\u0441\u0442\u0440\u0438\u0431\u0443\u0442\u0438\u0432\u0430\u0445 \u043c\u043e\u0436\u043d\u043e \u043e\u0446\u0435\u043d\u0438\u0442\u044c \u043d\u0430 \u0434\u0430\u043d\u043d\u044b\u0445 \u0441\u0442\u0440\u0430\u043d\u0438\u0446\u0430\u0445: Debian, Ubuntu, SUSE, RHEL, Arch \u0438 Fedora. \u0414\u043b\u044f \u0443\u0441\u0442\u0440\u0430\u043d\u0435\u043d\u0438\u044f \u043f\u0440\u043e\u0431\u043b\u0435\u043c [&hellip;]<\/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-149133","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=\"\u041e\u043f\u0443\u0431\u043b\u0438\u043a\u043e\u0432\u0430\u043d \u043d\u0430\u0431\u043e\u0440 \u043f\u0430\u0442\u0447\u0435\u0439 \u0441 \u0443\u0441\u0442\u0440\u0430\u043d\u0435\u043d\u0438\u0435\u043c 6 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0435\u0439 \u0432 \u0437\u0430\u0433\u0440\u0443\u0437\u0447\u0438\u043a\u0435 GRUB2, \u0431\u043e\u043b\u044c\u0448\u0438\u043d\u0441\u0442\u0432\u043e \u0438\u0437 \u043a\u043e\u0442\u043e\u0440\u044b\u0445 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