fbdev: core: Fix pointer desynchronization in fb_io_read()

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-80578
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-26 15:17:13 UTC
Updated2026-08-27 06:17:43 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: fbdev: core: Fix pointer desynchronization in fb_io_read() In fb_io_read(), if copy_to_user() performs a partial copy (e.g., due to a faulty user buffer), the loop adjusts the chunk size 'c' and updates the remaining 'count'. However, the hardware 'src' pointer has already been eagerly advanced by the original chunk size. If the loop is allowed to continue, the read will resume from an incorrect, over-advanced offset. Since the remaining 'count' was only decremented by the successful bytes, this desynchronization causes the next iterations to execute more hardware reads than originally bounded, eventually leading to out-of-bounds I/O reads. Fix this by breaking out of the loop immediately upon a partial copy_to_user(). A partial copy indicates a faulty user buffer, making subsequent read attempts futile. Breaking out ensures we return the number of successfully read bytes without risking out-of-bounds hardware accesses in subsequent mismatched iterations.

Risk And Classification

Primary CVSS: v3.1 7.3 HIGH from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H

EPSS: 0.001160000 probability, percentile 0.018130000 (date 2026-08-27)

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary7.3HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H
3.1CNADECLARED7.3HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
Low
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 6121cd9ef911432b14c2a17aefaf8cd2f3cfcdff 42bc07b4e5a3c8a02a433388f562a8f46d093e11 git Not specified
CNA Linux Linux affected 6121cd9ef911432b14c2a17aefaf8cd2f3cfcdff 42a6d8126c194133eafab2b0fd5c8668ebfcba5b git Not specified
CNA Linux Linux affected 6121cd9ef911432b14c2a17aefaf8cd2f3cfcdff 7ff87a01ae3a8cd0208f7499386998223a8b5dba git Not specified
CNA Linux Linux affected 6121cd9ef911432b14c2a17aefaf8cd2f3cfcdff 7110b7b794a2aac2c5cf8eb06ebf2af724c74d50 git Not specified
CNA Linux Linux affected 6121cd9ef911432b14c2a17aefaf8cd2f3cfcdff 81cc73be40c6f028f1ee3f438ace46afe666dbae git Not specified
CNA Linux Linux affected 6.5 Not specified
CNA Linux Linux unaffected 6.5 semver Not specified
CNA Linux Linux unaffected 6.6.153 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.105 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.46 6.18.* semver Not specified
CNA Linux Linux unaffected 7.1.10 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/7110b7b794a2aac2c5cf8eb06ebf2af724c74d50 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/81cc73be40c6f028f1ee3f438ace46afe666dbae 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/42bc07b4e5a3c8a02a433388f562a8f46d093e11 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/7ff87a01ae3a8cd0208f7499386998223a8b5dba 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/42a6d8126c194133eafab2b0fd5c8668ebfcba5b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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