CVE-2026-64600

Published Jul 23, 2026

Last updated 3 days ago

CVSS high 7.8

Overview

AI description

Automated description summarized from trusted sources.

CVE-2026-64600, also known as RefluXFS, is a race condition vulnerability found in the Linux kernel's XFS copy-on-write (CoW) path. This flaw allows an unprivileged local attacker to overwrite protected files on disk, potentially leading to the acquisition of host root privileges. The vulnerability arises when two concurrent `O_DIRECT` writes target the same reflinked file on an XFS filesystem with the `reflink` feature enabled. The core of the issue lies in the kernel temporarily dropping the inode lock while acquiring transaction resources. During this brief window, a second writer can modify the file's extent mapping. Consequently, the first writer proceeds with a stale physical-block mapping, leading to direct I/O writes using obsolete information and corrupting data belonging to the reflink source. This vulnerability has been present since Linux kernel version 4.11.

Description
In the Linux kernel, the following vulnerability has been resolved: xfs: resample the data fork mapping after cycling ILOCK xfs_reflink_fill_{cow_hole,delalloc} are both presented with an inode, a data fork mapping, and a cow fork mapping. Unfortunately, these two helpers cycle the ILOCK to grab a transaction, which means that the mappings are stale as soon as we reacquire the ILOCK. Currently we refresh the cow fork mapping by re-calling xfs_find_trim_cow_extent, but we don't refresh the data fork mapping beforehand, which means that the xfs_bmap_trim_cow in that function queries the refcount btree about the wrong physical blocks and returns an inaccurate value in *shared. If *shared is now false, the directio write proceeds with a stale data fork mapping. Fix this by querying the data fork mapping if the sequence counter changes across the ILOCK cycle.
Source
416baaa9-dc9f-4396-8d5f-8c081fb06d67
NVD status
Modified
Products
linux_kernel

Risk scores

CVSS 3.1

Type
Secondary
Base score
7.8
Impact score
5.9
Exploitability score
1.8
Vector string
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Severity
HIGH

Weaknesses

nvd@nist.gov
CWE-362
134c704f-9b21-4f2e-91b3-4a467353bcc0
CWE-362

Social media

Hype score
Not currently trending

  1. lpe-toolkit has been updated with new LPE exploits! New exploits added: - RefluXFS CVE-2026-64600 - CrackArmor CVE-2026-23268 - skb_shift CVE-2026-43503 - GRO Flag Loss CVE-2026-43503 - snap-confine CVE-2026-8933 https://t.co/Uafh1WjbqV

    @portbuster1337

    23 Sept 2026

    6594 Impressions

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  2. Qualys Says Claude Mythos Preview Helped Find CVE-2026-64600 in Linux XFS: On July 22, 2026, Qualys disclosed CVE-2026-64600, a race condition in XFS, a Linux filesystem. The flaw is in XFS's copy-on-write path, where the fil https://t.co/q539fFlZgx

    @vschmalbach

    29 Jul 2026

    3 Impressions

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  3. 🐧 π—”π—Ÿπ—˜π—₯𝗧𝗔 π—Ÿπ—œπ—‘π—¨π—«: 2 fallas crΓ­ticas de escalamiento de privilegios πŸ”Ή CVE-2026-8933 β†’ Ubuntu Desktop πŸ”Ή CVE-2026-64600 "RefluXFS" β†’ RHEL, CentOS, Rocky, AlmaLinux, Fedora, Amazon Linux MΓ‘s info πŸ‘‡πŸ‘‡ https://t.co/9PL0Ewg3GT #Ciberse

    @LeonelM41262107

    24 Jul 2026

    131 Impressions

    2 Retweets

    1 Like

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Configurations

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References

Sources include official advisories and independent security research.