# CVE-2026-64600 — Linux

> As of 2026-07-27, CVE-2026-64600 is a HIGH-severity vulnerability in Linux, CVSS v3.1 7.8, EPSS 0.4% (39.2th percentile). Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2026-64600, most recently “RefluXFS: Linux Kernel XFS Copy-on-Write Race Condition Local Privilege Escalation (CVE-2026-64600)”.

**Last updated:** 2026-07-27

## What is CVE-2026-64600?

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.

Its CVSS v3 base vector states that the flaw requires local access to the host, needs low-privilege credentials, needs no user interaction, and has high impact on confidentiality, integrity, availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 61 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 7.8 — HIGH (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **EPSS (FIRST):** 0.4% probability of exploitation in the next 30 days, higher than 39.2% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 7.5/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-07-23, last modified 2026-07-27

## Is CVE-2026-64600 being exploited?

Weaponised exploit code for CVE-2026-64600 is publicly available. 5 public proof-of-concept repositories are tracked for this identifier.

- [0xBlackash/CVE-2026-64600](https://github.com/0xBlackash/CVE-2026-64600) (github)
- [Debajyoti0-0/CVE-2026-64600](https://github.com/Debajyoti0-0/CVE-2026-64600) (github)
- [HORKimhab/CVE-2026-64600](https://github.com/HORKimhab/CVE-2026-64600) (github)
- [vulnquest58/VQ-RefluxCore](https://github.com/vulnquest58/VQ-RefluxCore) (github)
- [trickest/cve](https://github.com/trickest/cve/blob/main/2026/CVE-2026-64600.md) (trickest)

## Affected products and versions

- **Linux**: Linux

## How to fix CVE-2026-64600

No vendor patch reference has been recorded for CVE-2026-64600 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-64600

1 tracked threat in the Threadlinqs corpus references CVE-2026-64600, either in the campaign’s CVE list or as an indicator on the campaign record.

- [RefluXFS: Linux Kernel XFS Copy-on-Write Race Condition Local Privilege Escalation (CVE-2026-64600)](https://intel.threadlinqs.com/threat/TL-2026-1629) — HIGH · 2026-07-22

## Sources

Enriched from CVE.org, NVD, FIRST EPSS, GitHub Security Advisories, public proof-of-concept repositories. Last verified by Threadlinqs on 2026-07-28. This product uses the NVD API but is not endorsed or certified by the NVD.

**Other references**

- [git.kernel.org](https://git.kernel.org/stable/c/dc11be133efca5fe3a2fb02b016dee825cc12f18)
- [git.kernel.org (b8c9aa832b52680ee40d6cab0efb081f9a69df05)](https://git.kernel.org/stable/c/b8c9aa832b52680ee40d6cab0efb081f9a69df05)
- [git.kernel.org (50f0012da1040f69a4e788cd9aed587c9a04983f)](https://git.kernel.org/stable/c/50f0012da1040f69a4e788cd9aed587c9a04983f)
- [git.kernel.org (e705d81a7193dd19e69b8e2bad4696d78a4ea075)](https://git.kernel.org/stable/c/e705d81a7193dd19e69b8e2bad4696d78a4ea075)
- [git.kernel.org (206c09b04dc5469c7ff14d8aceff2d47c88078d9)](https://git.kernel.org/stable/c/206c09b04dc5469c7ff14d8aceff2d47c88078d9)

_Showing 5 of 8 recorded references._

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-64600
Full detection coverage and IOCs for threats exploiting CVE-2026-64600 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp