VulnerabilityPublished 25 Sep 2026Updated 21 Oct 2026

CVE-2026-98079: Linux kernel · btrfs: zstd: fix lost wakeup when waiting for a workspace

Affects Linux kernelSource CVE Database V5

Not known to be exploited · fixed in d8f57049521948df5f50797141472fbbed3b0723 : update Linux kernel when convenient.

Data as of 26 Oct 2026, 14:18 UTC

Severity

Unrated

Rated by Threat Radar · CVSS not yet scored by NVD

EPSS: 0.2% chance of exploitation in 30 days – higher than 9% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in d8f57049521948df5f50797141472fbbed3b0723, 844603cf842ee67640d33f350e3fa60f3de7fad3, 14d982762945d9945c60bbd48b77df194dd8e28d +2

Exploitation evidence

Disclosed: evidence found.
CVE published 25 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 ≥ 3f93aef535c8ea03e40cd8acf0753b3e6ed33e96, < d8f57049521948df5f50797141472fbbed3b0723	Fixed in d8f57049521948df5f50797141472fbbed3b0723
LinuxLinux	Affected ≥ 3f93aef535c8ea03e40cd8acf0753b3e6ed33e96, < 844603cf842ee67640d33f350e3fa60f3de7fad3	Fixed in 844603cf842ee67640d33f350e3fa60f3de7fad3
LinuxLinux	Affected ≥ 3f93aef535c8ea03e40cd8acf0753b3e6ed33e96, < 14d982762945d9945c60bbd48b77df194dd8e28d	Fixed in 14d982762945d9945c60bbd48b77df194dd8e28d
LinuxLinux	Affected ≥ 3f93aef535c8ea03e40cd8acf0753b3e6ed33e96, < 2acb9f3d1cc8f65dc81ed55e238cbf8e5b60bff7	Fixed in 2acb9f3d1cc8f65dc81ed55e238cbf8e5b60bff7
LinuxLinux	Affected ≥ 3f93aef535c8ea03e40cd8acf0753b3e6ed33e96, < 0de9f31d447ae71ab08c7850a321682f8d2907c3	Fixed in 0de9f31d447ae71ab08c7850a321682f8d2907c3
LinuxLinux	Affected =5.1	Fixed in–

Description

In the Linux kernel, the following vulnerability has been resolved: btrfs: zstd: fix lost wakeup when waiting for a workspace A writer can sleep forever in zstd_get_workspace() even though a workspace is free. When zstd_alloc_workspace() fails, the task is queued on zwsm->wait and schedules unconditionally, never re-testing the pool. zstd_put_workspace() publishes the workspace and then calls cond_wake_up(), which only wakes when a sleeper is already visible, so a workspace returned between the failed allocation and prepare_to_wait() wakes nobody. The window is wide: zstd_alloc_workspace() goes through kvmalloc() and may enter reclaim. Only a max level workspace triggers the wakeup and one is deliberately kept allocated as the fallback every waiter waits for, so once its wakeup is lost the writer stays in TASK_UNINTERRUPTIBLE until some other task happens to return one. Re-check the pool after prepare_to_wait() has published the waiter, and use the workspace if one turned up.

References

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