Bug 2477015 (CVE-2026-46300)
| Summary: | CVE-2026-46300 kernel: "Fragnesia" is a variant of Dirty Frag vulnerability in the ESP/XFRM leading to Local Privilege Escalation (LPE) vulnerability in the Linux kernel | ||
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| Product: | [Other] Security Response | Reporter: | OSIDB Bzimport <bzimport> |
| Component: | vulnerability | Assignee: | Product Security <prodsec-ir-bot> |
| Status: | NEW --- | QA Contact: | |
| Severity: | high | Docs Contact: | |
| Priority: | high | ||
| Version: | unspecified | CC: | akoudelk, alcohan, alinfoot, asoldano, astupnik, bbaranow, bbrownin, bdettelb, bmaxwell, bstansbe, cchiang, dlofthou, doconnor, dtrifiro, dymurray, eric.eisenhart, fdeutsch, fmariani, gmalinko, gparvin, istudens, ivassile, iweiss, janstey, jbalunas, jkoehler, jmatthew, jmitchel, jwon, kbempah, kevinxue, kshier, lbragsta, lchilton, lphiri, manissin, mcarlett, mosmerov, msvehla, nwallace, oramraz, pahickey, pberan, pbohmill, pdelbell, pesilva, pjindal, pjs1, pmackay, rbryant, rhaigner, rhel-process-autobot, rjohnson, rstancel, rstepani, sardella, sfeifer, smaestri, smullick, solenoci, stirabos, tcunning, teagle, thason, thjenkin, vdosoudi, victor.cardoso, villapla, watson-tool-maintainers, weaton, wenshen, whayutin, xiyuan, yfang |
| Target Milestone: | --- | Keywords: | Security |
| Target Release: | --- | ||
| Hardware: | All | ||
| OS: | Linux | ||
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| Fixed In Version: | Doc Type: | --- | |
| Doc Text: |
A flaw was found in the Linux kernel's XFRM ESP-in-TCP subsystem. Unsafe in-place cryptographic processing allows a low-privileged local attacker to write arbitrary bytes into the page cache of read-only files, including sensitive system files. An attacker can exploit this to overwrite privileged binaries and gain root privileges.
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Story Points: | --- |
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| Last Closed: | Type: | --- | |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
| Embargoed: | |||
Fragnesia is a universal Linux local privilege escalation exploit, discovered by William Bowling with the V12 team. Fragnesia is a member of the Dirty Frag vulnerability class. This is a separate bug in the ESP/XFRM from dirtyfrag which has received its own patch. However, it is in the same surface and the mitigation is the same as for dirtyfrag. It abuses a logic bug in the Linux XFRM ESP-in-TCP subsystem to achieve arbitrary byte writes into the kernel page cache of read-only files, without requiring any race condition. The technique extends the page-cache write bug class that includes Dirty Pipe: when a TCP socket transitions to espintcp ULP mode after data has already been spliced from a file into the receive queue, the kernel processes the queued file pages as ESP ciphertext. The AES-GCM keystream byte at counter block position 2, byte 0 is XORed directly into the cached file page. By selecting the IV nonce to produce a desired keystream byte, any target byte in the file can be set to any value — one byte per trigger invocation. The exploit builds a 256-entry lookup table mapping each possible keystream byte to its corresponding nonce, then iterates over a payload, firing the splice/ULP race for each byte that needs changing. It writes a small position-independent ELF stub (setresuid/setresgid/execve /bin/sh) over the first 192 bytes of /usr/bin/su in the page cache, then calls execve("/usr/bin/su") to obtain a root shell. The page cache modification is not backed to disk; the on-disk binary is untouched.