{"id":181735,"date":"2026-05-25T20:48:34","date_gmt":"2026-05-25T18:48:34","guid":{"rendered":"https:\/\/prohoster.info\/blog\/novosti-interneta\/gro-frag-novaya-lpe-uyazvimost-v-setevom-steke-linux-pozvolyaet-poluchit-root"},"modified":"2026-05-25T20:48:34","modified_gmt":"2026-05-25T18:48:34","slug":"gro-frag-novaya-lpe-uyazvimost-v-setevom-steke-linux-pozvolyaet-poluchit-root","status":"publish","type":"post","link":"https:\/\/prohoster.info\/hr\/blog\/news\/gro-frag-novaya-lpe-uyazvimost-v-setevom-steke-linux-pozvolyaet-poluchit-root","title":{"rendered":"GRO Frag: nova LPE ranjivost u mre\u017enom steku Linux omogu\u0107uje dobivanje root privilegija","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

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Objavljen je exploit za GRO Frag<\/strong> \u2014 lokalnu ranjivost za pove\u0107anje privilegija u Linux kernelu, povezanom s obradom GRO i zero-copy skb u mre\u017enom stogu. To\u010dan datum prvotnog otkrivanja u javnim materijalima nije naveden<\/strong>. Prema dostupnim informacijama, mo\u017eemo zabilje\u017eiti dvije datume: ispravak se raspravljao na mailing listi netdev 20. svibnja 2026. godine<\/strong>, gdje je ova ranjivost ve\u0107 opisana kao pogodna za prepisivanje page cachea, a javni PoC postavljen je na GitHub Gist<\/a> 22. svibnja 2026. godine<\/strong>.<\/p>\n

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Kao privremena mjera do instalacije ispravljenog kernela, mo\u017ee se ograni\u010diti vektor napada putem sysctl: kernel.io_uring_disabled=1. Ovaj na\u010din onemogu\u0107uje kreiranje novih instanci io_uring od strane neprivilegiranih procesa, osim ako nisu uklju\u010deni u dozvoljenu grupu io_uring_group; za vrijednost grupe -1 dostupnost zadr\u017eavaju samo procesi s CAP_SYS_ADMIN. Ovo je mitigacija, a ne potpuno ispravljanje ranjivosti.<\/p>\n

Problem se nalazi u funkciji skb_gro_receive(): pri spajanju GRO paketa, kernel je mogao premjestiti fragmente iz zero-copy skb u drugi skb bez pravilne provjere stanja zero-copy i oznake SKBFL_MANAGED_FRAG_REFS. Kao rezultat, stranice memorije kojima izvorni skb nije dr\u017eao zasebne reference, mogle su biti oslobo\u0111ene neispravno, \u0161to je dovodilo do use-after-free. U patchu se izravno navodi da takva situacija mo\u017ee dovesti do UAF, kao i da je prona\u0111ena varijanta pogodna za prepisivanje page cachea.<\/p>\n

<\/p>\n

Objavljeni PoC opisuje ranjivost kao LPE preko GRO managed-frag UAF<\/strong> koriste\u0107i io_uring SEND_ZC i virtualno mre\u017eno su\u010delje veth. U komentaru koda se navodi da su pogo\u0111eni kerneli Linux 6.0+<\/strong>, eksploatacija je mogu\u0107a od strane neprivilegiranog korisnika, ali zahtijeva dostupni io_uring; kao ispravak se navodi commit<\/a> 4db79a322db8 s promjenom \u00abnet: gro: nemojte spojiti zcopy skbs\u00bb.<\/p>\n

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\n<\/p>\n

U posljedicama, GRO Frag se uklapa u istu opasnu klasu gre\u0161aka kao Copy Fail i Dirty Frag: napada\u010d s lokalnim neprivilegiranim pristupom mo\u017ee promijeniti podatke u page cacheu, tj. u memoriji, bez obvezne modifikacije datoteke na disku. Ove vrste gre\u0161aka su posebno neugodnih jer se odnose na granicu izme\u0111u \u00absamo za \u010ditanje\u00bb datoteke i stvarnog sadr\u017eaja koji kernel i procesi vide prilikom narednih pristupa. Elastic ranije je opisao<\/a> ovu klasu kao prakti\u010dan put za dobivanje root pristupa putem o\u0161te\u0107enja page-cachea.<\/p>\n

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U trenutku objave, posebni CVE identifikator za GRO Frag, prema dostupnim informacijama, jo\u0161 nije bio dodeljen. Kao privremenu meru, administratorima se savetuje da a\u017euriraju jezgro na verziju sa ispravkom, kao i da primene op\u0161te mere za smanjenje rizika od sli\u010dnih LPE: ograni\u010davanje nepriviligovanih korisni\u010dkih prostora gde je to mogu\u0107e, kontrola kori\u0161\u0107enja io_uring i pra\u0107enje sumnjivih lanaca povezanih sa lokalnom eskalacijom privilegija. Za srodne Copy Fail\/DirtyFrag napade, Elastic tako\u0111e preporu\u010duje kombinovanje zakrivanja sa detekcijom niskonivoa primitvnih eksploata.<\/p>\n

Niskonivoi primitivni eksploati nisu sami po sebi \"gotov hack\", ve\u0107 osnovne tehni\u010dke tehnike od kojih se gradi eksploat.<\/p>\n

U kontekstu GRO Frag, to mo\u017ee zna\u010diti ne detektovanje ve\u0107 gotovog slu\u010daja \"korisnik postao root\", ve\u0107 poku\u0161aj uo\u010davanja pojedina\u010dnih sumnjivih radnji koje eksploat koristi na putu ka pove\u0107anju privilegija.<\/p>\n

Izvor: linux.org.ru<\/a><\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

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