VulnerabilityPublished 19 Jul 2026Updated 11 Sep 2026

CVE-2026-63820: Linux kernel · f2fs: fix missing read bio submission on large folio error

Affects Linux kernelSource GCVE Database

Not known to be exploited · fixed in 7.0.0-31.31~24.04.1 : update Linux kernel when convenient.

Data as of 26 Oct 2026, 14:05 UTC

Severity

Medium

Rated by Threat Radar · No CVSS score from NVD or the CNA

EPSS: 0.1% 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 7.0.0-31.31~24.04.1, 7.0.0-31.31, 7.0.0-1012.12 +7

Exploitation evidence

Disclosed: evidence found.
CVE published 19 Jul 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
Ubuntu 26.04 LTSlinux`pkg:deb/ubuntu/linux?arch=source&distro=resolute`Other threats	Affected <7.0.0-31.31	Fixed in 7.0.0-31.31
Ubuntu 26.04 LTSlinux-aws`pkg:deb/ubuntu/linux-aws?arch=source&distro=resolute`Other threats	Affected <7.0.0-1012.12	Fixed in 7.0.0-1012.12
Ubuntu 26.04 LTSlinux-azure`pkg:deb/ubuntu/linux-azure?arch=source&distro=resolute`Other threats	Affected 6.17.0-1003.3 – 7.0.0-1012.12 13 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-azure-fde`pkg:deb/ubuntu/linux-azure-fde?arch=source&distro=resolute`Other threats	Affected 7.0.0-1003.3 – 7.0.0-1011.11 7 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-gcp`pkg:deb/ubuntu/linux-gcp?arch=source&distro=resolute`Other threats	Affected <7.0.0-1011.11	Fixed in 7.0.0-1011.11
Ubuntu 26.04 LTSlinux-gke`pkg:deb/ubuntu/linux-gke?arch=source&distro=resolute`Other threats	Affected <7.0.0-1006.7	Fixed in 7.0.0-1006.7

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A patch is available and should be applied to affected Linux kernel versions. The vendor advisory from Ubuntu confirms that this issue has been fixed in updated kernel packages. Users should update to the fixed kernel versions as provided by their distribution to resolve this issue.

Description

A vulnerability in the Linux kernel's f2fs file system was fixed that could cause read operations to hang indefinitely. The issue involved missing submission of read bio requests when errors occurred on large folios during readahead, leading to locked folios that never complete. This flaw was addressed by ensuring any pending bio is submitted before returning on error and stopping further readahead processing once an error is detected.

Impact

Affected systems could experience indefinite blocking of read operations on the f2fs file system due to unsubmitted read bio requests when errors occur on large folios. This could lead to system hangs or degraded performance for processes reading from f2fs volumes. There is no indication of privilege escalation or remote code execution from this vulnerability.

Summary

The Linux kernel's f2fs_read_data_large_folio() function could keep a read bio across multiple readahead folios. If a later folio encountered an error before any blocks were added to the bio, the error path would return immediately after ending that folio without submitting the accumulated bio for earlier folios. This caused those folios to never receive read completion, potentially causing readers to wait indefinitely on locked folios. The fix routes errors through a common exit path to submit any pending bio before returning and stops consuming more readahead folios once an error is seen, waiting only on folios actually added to the bio.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 25 Oct 2026, 12:32 UTC

Technical details

References

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