{"id":"CVE-2026-56857","state":"PUBLISHED","title":"Root.Mkdir(All) can follow junctions out of the root on Windows in os","description":"On Windows, when the target of Root.Mkdir or Root.MkdirAll is a junction pointing to an empty location, the operation can create a directory at the junction target even when that target is located outside the root. This only applies to operations where the last path component is a junction (path/to/junction, but not path/junction/target).","publishedAt":"2026-10-08T22:53:58.387Z","updatedAt":"2026-10-09T15:36:01.712Z","severity":{"score":9.8,"label":"Critical","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","source":"CISA-ADP"},"assigner":"Go","products":["Go standard library os","Go standard library internal/syscall/windows"],"affected":[{"vendor":"Go standard library","product":"os","packageName":"os","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThan":"1.26.9","versionType":"semver"},{"version":"1.27.0-0","status":"affected","lessThan":"1.27.2","versionType":"semver"}],"collectionURL":"https://pkg.go.dev","platforms":["windows"],"programRoutines":[{"name":"Root.Mkdir"},{"name":"doInRoot"},{"name":"rootMkdirAll"},{"name":"Root.Chmod"},{"name":"Root.Chown"},{"name":"Root.Chtimes"},{"name":"Root.Lchown"},{"name":"Root.Link"},{"name":"Root.MkdirAll"},{"name":"Root.Remove"},{"name":"Root.RemoveAll"},{"name":"Root.Rename"},{"name":"Root.Symlink"}]},{"vendor":"Go standard library","product":"internal/syscall/windows","packageName":"internal/syscall/windows","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThan":"1.26.9","versionType":"semver"},{"version":"1.27.0-0","status":"affected","lessThan":"1.27.2","versionType":"semver"}],"collectionURL":"https://pkg.go.dev","platforms":["windows"],"programRoutines":[{"name":"Mkdirat"}]}],"references":["https://go.dev/cl/847305","https://go.dev/issue/81739","https://groups.google.com/g/golang-announce/c/U2fTuyDJznI","https://pkg.go.dev/vuln/GO-2026-6604"],"weaknesses":["CWE-1386"],"ingestedAt":"2026-10-29T20:12:24.861Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/56xxx/CVE-2026-56857.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-56857","state":"PUBLISHED","datePublished":"2026-10-08T22:53:58.387Z","dateUpdated":"2026-10-09T15:36:01.712Z","assignerShortName":"Go","assignerOrgId":"1bb62c36-49e3-4200-9d77-64a1400537cc","dateReserved":"2026-06-23T15:10:49.353Z"},"containers":{"cna":{"title":"Root.Mkdir(All) can follow junctions out of the root on Windows in os","descriptions":[{"lang":"en","value":"On Windows, when the target of Root.Mkdir or Root.MkdirAll is a junction pointing to an empty location, the operation can create a directory at the junction target even when that target is located outside the root. This only applies to operations where the last path component is a junction (path/to/junction, but not path/junction/target)."}],"affected":[{"vendor":"Go standard library","product":"os","packageName":"os","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThan":"1.26.9","versionType":"semver"},{"version":"1.27.0-0","status":"affected","lessThan":"1.27.2","versionType":"semver"}],"collectionURL":"https://pkg.go.dev","platforms":["windows"],"programRoutines":[{"name":"Root.Mkdir"},{"name":"doInRoot"},{"name":"rootMkdirAll"},{"name":"Root.Chmod"},{"name":"Root.Chown"},{"name":"Root.Chtimes"},{"name":"Root.Lchown"},{"name":"Root.Link"},{"name":"Root.MkdirAll"},{"name":"Root.Remove"},{"name":"Root.RemoveAll"},{"name":"Root.Rename"},{"name":"Root.Symlink"}]},{"vendor":"Go standard library","product":"internal/syscall/windows","packageName":"internal/syscall/windows","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThan":"1.26.9","versionType":"semver"},{"version":"1.27.0-0","status":"affected","lessThan":"1.27.2","versionType":"semver"}],"collectionURL":"https://pkg.go.dev","platforms":["windows"],"programRoutines":[{"name":"Mkdirat"}]}],"references":[{"url":"https://go.dev/cl/847305"},{"url":"https://go.dev/issue/81739"},{"url":"https://groups.google.com/g/golang-announce/c/U2fTuyDJznI"},{"url":"https://pkg.go.dev/vuln/GO-2026-6604"}],"problemTypes":[{"descriptions":[{"lang":"en","description":"CWE-1386: Insecure Operation on Windows Junction / Mount Point"}]}],"providerMetadata":{"shortName":"Go","orgId":"1bb62c36-49e3-4200-9d77-64a1400537cc","dateUpdated":"2026-10-08T22:53:58.387Z"},"credits":[{"lang":"en","value":"Daniele Ballarini"}]},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"cvssV3_1":{"scope":"UNCHANGED","version":"3.1","baseScore":9.8,"attackVector":"NETWORK","baseSeverity":"CRITICAL","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","integrityImpact":"HIGH","userInteraction":"NONE","attackComplexity":"LOW","availabilityImpact":"HIGH","privilegesRequired":"NONE","confidentialityImpact":"HIGH"}},{"other":{"type":"ssvc","content":{"timestamp":"2026-10-09T15:35:58.663117Z","id":"CVE-2026-56857","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-1386","type":"CWE","lang":"en","description":"CWE-1386 Insecure Operation on Windows Junction / Mount Point"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-09T15:36:01.712Z"}}]}}}