CVE-2026-64593: btrfs: do not trim a device which is not writeable

criticalCVSS 9.8CVE-2026-64593

CSIRTS triage

product: Linux kernel btrfs Privilege escalation

What: A race condition allows trimming operations on non-writable block devices, potentially enabling privilege escalation or filesystem corruption.
Who is affected: Systems running Linux kernel with btrfs filesystem, especially with write restrictions in place.
Urgency: Critical with CVSS 9.8; immediate patching is required.
Action: Update the Linux kernel to a version containing the btrfs trim validation fix.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: critical — CVSS 9.8
Published: 2026-08-11
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-64593

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-645930.16% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 6% of all EPSS-scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-64593	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

Recent advisories for btrfs

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

highCVE-2026-74572: In the Linux kernel, the following vulnerability has been resolved: btrfs: zoned: fix deadlock…nvd · 2026-08-15
unknownCVE-2026-74571: In the Linux kernel, the following vulnerability has been resolved: btrfs: skip global block r…nvd · 2026-08-15
highCVE-2026-74321: In the Linux kernel, the following vulnerability has been resolved: btrfs: fix invalid pointer…nvd · 2026-08-15
unknownCVE-2026-74319: In the Linux kernel, the following vulnerability has been resolved: btrfs: zoned: fix deadlock…nvd · 2026-08-15
unknownCVE-2026-74318: In the Linux kernel, the following vulnerability has been resolved: btrfs: fix deadlock clonin…nvd · 2026-08-15
unknownCVE-2026-68450: In the Linux kernel, the following vulnerability has been resolved: btrfs: free mapping node o…nvd · 2026-08-12