TOCTOU permits root escape on Linux via Root.Chmod in os in internal/syscall/unix (Go standard library internal/syscall/unix)
At a glance
- Source
- NVD
- EPSS
- EPSS 0.29 % · percentile 22 ()
- State
- PUBLISHED
- Published
- Updated
- Assigner
- Go
- NVD status
- Analyzed
Description
On 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.
Weaknesses (CWE)
- CWE-59 — Improper Link Resolution Before File Access
References
Scores
| Version | Score | Vector | Scored by |
|---|---|---|---|
| CVSS 3.1 | MEDIUM 6.4 | CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H | CISA-ADP |
| CVSS 3.1 | MEDIUM 6.4 | CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H | NVD · nvd@nist.gov (Primary) |
| CVSS 3.1 | MEDIUM 6.4 | CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H | NVD · 134c704f-9b21-4f2e-91b3-4a467353bcc0 (Secondary) |
Advisories
- GO-2026-4864 — TOCTOU permits root escape on Linux via Root.Chmod in os in internal/syscall/unix
European references
- ENISA EUVD · EUVD-2026-20012
- GCVE · GCVE-0-2026-32282
CERT-FR advisories
- CERTFR-2026-AVI-1385 — Multiples vulnérabilités dans les produits VMware · cert.ssi.gouv.fr
- CERTFR-2026-AVI-1281 — Multiples vulnérabilités dans les produits Splunk · cert.ssi.gouv.fr
- CERTFR-2026-AVI-1249 — Multiples vulnérabilités dans les produits VMware · cert.ssi.gouv.fr
- CERTFR-2026-AVI-0627 — Multiples vulnérabilités dans les produits Splunk · cert.ssi.gouv.fr
- CERTFR-2026-AVI-0556 — Multiples vulnérabilités dans les produits VMware · cert.ssi.gouv.fr
- CERTFR-2026-AVI-0540 — Multiples vulnérabilités dans VMware Tanzu Gemfire · cert.ssi.gouv.fr
- CERTFR-2026-AVI-0498 — Multiples vulnérabilités dans Zabbix Agent2 · cert.ssi.gouv.fr
Affected configurations (NVD CPE)
cpe:2.3:a:golang:go:*:*:*:*:*:*:*:*< 1.25.9cpe:2.3:a:golang:go:*:*:*:*:*:*:*:*≥ 1.26.0 < 1.26.2
Affected products
| Product | Versions |
|---|---|
| Go standard library · internal/syscall/unix | affected 0 < 1.25.9 ; affected 1.26.0-0 < 1.26.2 |
Sources
| Source | Licence |
|---|---|
| CVE List (CVEProject cvelistV5) | CVE Program Terms of Use |
| EPSS (FIRST.org) | FIRST — attribution requested |
| ENISA EUVD | ENISA — reproduction authorised, source acknowledged |
| CERT-FR (ANSSI) | Licence Ouverte / Etalab 2.0 |
| NVD (NIST) via fkie-cad/nvd-json-data-feeds | Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD |