CVE-2026-64567: btrfs: reject free space cache with more entries than pages

mediumCVSS 4.4CVE-2026-64567

CSIRTS triage

product: Linux kernel (btrfs)Denial of service

What: Btrfs rejects free space cache with more entries than pages can accommodate, preventing filesystem operations.
Who is affected: Systems using btrfs filesystems with corrupted or maliciously crafted free space cache metadata.
Urgency: Medium urgency; denial of service can prevent filesystem access but requires ability to write crafted cache metadata.
Action: Apply Linux kernel patch enforcing entry count validation in btrfs free space cache parsing.

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

⚡ Watch Linux kernel (btrfs)

Get an email when a new Linux kernel (btrfs) advisory drops — max one per day, one-click unsubscribe.

Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: medium — CVSS 4.4
Published: 2026-08-11
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-64567

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-2026-645670.12% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 2% of all EPSS-scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-64567	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

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

unknownMultiple vulnerabilities in Debian Linux kernel (August 14, 2026)cert-fr-avis
medium[UPDATE] [medium] Linux Kernel: Multiple vulnerabilitiescert-bund
unknownDSA-6415-1 linux - security updatedebian
highCVE-2026-64567: In the Linux kernel, the following vulnerability has been resolved: btrfs: reject free space c…nvd

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.

unknownCVE-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
unknownCVE-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