VulnerabilityPublished 19 Jul 2026

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

Source GCVE Database

Not known to be exploited.

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.

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.

ghsa-m33g-hj44-mvvf

What to do

AI-suggested

A fix has been implemented in the Linux kernel to address this issue. Users should apply the official kernel updates that include this patch to resolve the vulnerability. Since this is not a cloud service, remediation depends on applying the updated kernel version. Patch status is not explicitly confirmed in the provided data; users should consult the Linux kernel vendor advisory for the exact fixed versions and update accordingly.

Description

A vulnerability in the Linux kernel's f2fs filesystem was resolved that involved missing submission of read bio operations on large folio read errors. The issue could cause read bio operations to remain unsubmitted when an error occurs on a later folio, leading to indefinite waits on locked folios by readers. The fix ensures that any pending bio is submitted before returning on error and stops further readahead folios consumption once an error is detected.

Impact

Affected systems running the vulnerable Linux kernel could experience indefinite blocking on read operations involving the f2fs filesystem due to unsubmitted read bio operations. This could lead to system hangs or degraded performance when reading large files under error conditions. No known exploits in the wild have been reported.

Summary

The vulnerability in the Linux kernel's f2fs_read_data_large_folio() function allowed a read bio to be kept across multiple readahead folios. If a later folio encountered an error before its blocks were added to the bio, the error path would return immediately without submitting the accumulated bio for earlier folios. This caused those folios to never receive read completion, potentially causing indefinite blocking on locked folios. The patch routes errors through a common exit path to ensure any pending bio is submitted before returning, and halts further readahead folio processing upon error detection.

References

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