TOCTOU permits root escape on Linux via Root.Chmod in os in internal/syscall/unix

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Summary

CVECVE-2026-32282
StatePUBLISHED
AssignerGo
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-08 02:16:03 UTC
Updated2026-04-16 19:15:39 UTC
DescriptionOn Linux, if the target of Root.Chmod is replaced with a symlink while the chmod operation is in progress, Chmod can operate on the target of the symlink, even when the target lies outside the root. The Linux fchmodat syscall silently ignores the AT_SYMLINK_NOFOLLOW flag, which Root.Chmod uses to avoid symlink traversal. Root.Chmod checks its target before acting and returns an error if the target is a symlink lying outside the root, so the impact is limited to cases where the target is replaced with a symlink between the check and operation.

Risk And Classification

Primary CVSS: v3.1 6.4 MEDIUM from [email protected]

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

EPSS: 0.000080000 probability, percentile 0.007730000 (date 2026-04-15)

Problem Types: CWE-59 | CWE-61: UNIX Symbolic Link (Symlink) Following

VersionSourceTypeScoreSeverityVector
3.1[email protected]Primary6.4MEDIUMCVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H
3.1ADPDECLARED6.4MEDIUMCVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H
3.1134c704f-9b21-4f2e-91b3-4a467353bcc0Secondary6.4MEDIUMCVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

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

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

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Golang Go All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Go Standard Library Internal/syscall/unix affected 1.25.9 semver linux
CNA Go Standard Library Internal/syscall/unix affected 1.26.0-0 1.26.2 semver linux

References

ReferenceSourceLinkTags
pkg.go.dev/vuln/GO-2026-4864 [email protected] pkg.go.dev Vendor Advisory
go.dev/issue/78293 [email protected] go.dev Issue Tracking
groups.google.com/g/golang-announce/c/0uYbvbPZRWU [email protected] groups.google.com Release Notes, Mailing List
go.dev/cl/763761 [email protected] go.dev Patch
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Uuganbayar Lkhamsuren (https://github.com/uug4na) (en)

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