VulnerabilityPublished 11 Sep 2026Updated 21 Oct 2026

CVE-2026-89644: Linux kernel · btrfs: fix extent map leak in NOCOW direct I/O write

Affects Linux kernelSource CVE Database V5

Not known to be exploited · fixed in f42efd634c0ae7ba0ce2fc5e30e291b0803b0ae2 : update Linux kernel when convenient.

Data as of 26 Oct 2026, 13:47 UTC

Severity

Unrated

Rated by Threat Radar · CVSS not yet scored by NVD

EPSS: 0.1% chance of exploitation in 30 days – higher than 6% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in f42efd634c0ae7ba0ce2fc5e30e291b0803b0ae2, cb732d302245b14943a5017015fffa8e6db7a6c0, b7c873765875645b11503f94c9bae2ca80127375 +2

Exploitation evidence

Disclosed: evidence found.
CVE published 11 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 5f9a8a51d8b95505d8de8b7191ae2ed8c504d4af, < f42efd634c0ae7ba0ce2fc5e30e291b0803b0ae2	Fixed in f42efd634c0ae7ba0ce2fc5e30e291b0803b0ae2
LinuxLinux	Affected ≥ 5f9a8a51d8b95505d8de8b7191ae2ed8c504d4af, < cb732d302245b14943a5017015fffa8e6db7a6c0	Fixed in cb732d302245b14943a5017015fffa8e6db7a6c0
LinuxLinux	Affected ≥ 5f9a8a51d8b95505d8de8b7191ae2ed8c504d4af, < b7c873765875645b11503f94c9bae2ca80127375	Fixed in b7c873765875645b11503f94c9bae2ca80127375
LinuxLinux	Affected ≥ 5f9a8a51d8b95505d8de8b7191ae2ed8c504d4af, < 05a1a816eef8b3e4332620a64fc8cf45c4eb5c0d	Fixed in 05a1a816eef8b3e4332620a64fc8cf45c4eb5c0d
LinuxLinux	Affected ≥ 5f9a8a51d8b95505d8de8b7191ae2ed8c504d4af, < 3f950867c307c5413d628a153ac44915bd117ffd	Fixed in 3f950867c307c5413d628a153ac44915bd117ffd
LinuxLinux	Affected =4.7	Fixed in–

Description

In the Linux kernel, the following vulnerability has been resolved: btrfs: fix extent map leak in NOCOW direct I/O write btrfs_dio_iomap_begin() calls btrfs_get_extent(), which returns an extent map reference that must be dropped on all exit paths. For direct writes into a NOCOW range, btrfs_get_blocks_direct_write() keeps using that extent map and asks btrfs_create_dio_extent() to allocate the ordered extent. If that fails, for example because btrfs_alloc_ordered_extent() fails, the function returns the error without dropping the input extent map. The PREALLOC path avoided this by dropping the input extent map before replacing it with the newly created one. Check the error from btrfs_create_dio_extent() before replacing the map and drop the input extent map on failure.

References

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