CVE-2026-43308: btrfs: don't BUG() on unexpected delayed ref type in run_one_delayed_ref()

mediumCVSS 5.5CVE-2026-43308

CSIRTS triage

vendor: Linux product: Linux kernel btrfs Denial of service

What: The btrfs run_one_delayed_ref() function triggers a BUG() panic on unexpected delayed ref types instead of handling the error gracefully.
Who is affected: Linux systems using btrfs filesystem.
Urgency: Medium; DoS via kernel panic is severe but requires specific btrfs state.
Action: Apply kernel patch that replaces BUG() with proper error handling.

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: medium — CVSS 5.5
Published: 2026-08-06
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-43308

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-2026-433080.11% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 1% of all EPSS-scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-43308	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

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

medium[UPDATE] [medium] Linux Kernel: Multiple vulnerabilitiescert-bund
unknownexploitedMultiple vulnerabilities in SUSE Linux kernel (August 14, 2026)cert-fr-avis

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