{"id":"CVE-2026-78409","state":"PUBLISHED","title":"Util-linux: util-linux: x-mount.subdir detached-tree resolution can escape via intermediate symlinks","description":"The X-mount.subdir option uses a detached-tree fast path on Linux 6.15 and later and passes the configured subdirectory to open_tree() with AT_SYMLINK_NOFOLLOW. That flag does not stop intermediate symlink traversal or keep resolution inside the newly mounted filesystem. A local unprivileged user with an fstab-authorized X-mount.subdir entry can attach a host path at the intended mountpoint.","publishedAt":"2026-09-02T15:11:47.184Z","updatedAt":"2026-10-21T17:51:49.053Z","severity":{"score":7,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"redhat"},"assigner":"redhat","products":["Red Hat Red Hat Hardened Images","Red Hat Red Hat Enterprise Linux 10","Red Hat Red Hat Enterprise Linux 7","Red Hat Red Hat Enterprise Linux 8","Red Hat Red Hat Enterprise Linux 9","Red Hat Red Hat OpenShift Container Platform 4"],"affected":[{"vendor":"Red Hat","product":"Red Hat Hardened Images","packageName":"util-linux-main","defaultStatus":"affected","versions":[{"version":"2.42.2-3.4.hum1","status":"unaffected","lessThan":"*","versionType":"rpm"}],"collectionURL":"https://catalog.redhat.com/software/containers/","cpes":["cpe:/a:redhat:hummingbird:1"]},{"vendor":"Red Hat","product":"Red Hat Enterprise Linux 10","packageName":"util-linux","defaultStatus":"unaffected","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/o:redhat:enterprise_linux:10"]},{"vendor":"Red Hat","product":"Red Hat Enterprise Linux 7","packageName":"util-linux","defaultStatus":"unaffected","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/o:redhat:enterprise_linux:7"]},{"vendor":"Red Hat","product":"Red Hat Enterprise Linux 8","packageName":"util-linux","defaultStatus":"unaffected","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/o:redhat:enterprise_linux:8"]},{"vendor":"Red Hat","product":"Red Hat Enterprise Linux 9","packageName":"rhel8/flatpak-runtime","defaultStatus":"unaffected","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/o:redhat:enterprise_linux:9"]},{"vendor":"Red Hat","product":"Red Hat Enterprise Linux 9","packageName":"rhel8/flatpak-sdk","defaultStatus":"unaffected","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/o:redhat:enterprise_linux:9"]},{"vendor":"Red Hat","product":"Red Hat Enterprise Linux 9","packageName":"util-linux","defaultStatus":"unaffected","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/o:redhat:enterprise_linux:9"]},{"vendor":"Red Hat","product":"Red Hat OpenShift Container Platform 4","packageName":"openshift/ose-rhel-coreos-8","defaultStatus":"unaffected","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/a:redhat:openshift:4"]},{"vendor":"Red Hat","product":"Red Hat OpenShift Container Platform 4","packageName":"openshift/ose-rhel-coreos-9","defaultStatus":"unaffected","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/a:redhat:openshift:4"]}],"references":["https://access.redhat.com/errata/RHSA-2026:63162","https://access.redhat.com/security/cve/CVE-2026-78409","https://bugzilla.redhat.com/show_bug.cgi?id=2522607","https://github.com/util-linux/util-linux/security/advisories/GHSA-8f2p-47x3-43mv"],"weaknesses":["CWE-59"],"ingestedAt":"2026-10-29T20:13:07.220Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/78xxx/CVE-2026-78409.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-78409","state":"PUBLISHED","datePublished":"2026-09-02T15:11:47.184Z","dateUpdated":"2026-10-21T17:51:49.053Z","assignerShortName":"redhat","assignerOrgId":"53f830b8-0a3f-465b-8143-3b8a9948e749","dateReserved":"2026-08-24T14:40:18.012Z"},"containers":{"cna":{"title":"Util-linux: util-linux: x-mount.subdir detached-tree resolution can escape via intermediate symlinks","descriptions":[{"lang":"en","value":"The X-mount.subdir option uses a detached-tree fast path on Linux 6.15 and later and passes the configured subdirectory to open_tree() with AT_SYMLINK_NOFOLLOW. That flag does not stop intermediate symlink traversal or keep resolution inside the newly mounted filesystem. A local unprivileged user with an fstab-authorized X-mount.subdir entry can attach a host path at the intended mountpoint."}],"affected":[{"vendor":"Red Hat","product":"Red Hat Hardened Images","packageName":"util-linux-main","defaultStatus":"affected","versions":[{"version":"2.42.2-3.4.hum1","status":"unaffected","lessThan":"*","versionType":"rpm"}],"collectionURL":"https://catalog.redhat.com/software/containers/","cpes":["cpe:/a:redhat:hummingbird:1"]},{"vendor":"Red Hat","product":"Red Hat Enterprise Linux 10","packageName":"util-linux","defaultStatus":"unaffected","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/o:redhat:enterprise_linux:10"]},{"vendor":"Red Hat","product":"Red Hat Enterprise Linux 7","packageName":"util-linux","defaultStatus":"unaffected","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/o:redhat:enterprise_linux:7"]},{"vendor":"Red Hat","product":"Red Hat Enterprise Linux 8","packageName":"util-linux","defaultStatus":"unaffected","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/o:redhat:enterprise_linux:8"]},{"vendor":"Red Hat","product":"Red Hat Enterprise Linux 9","packageName":"rhel8/flatpak-runtime","defaultStatus":"unaffected","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/o:redhat:enterprise_linux:9"]},{"vendor":"Red Hat","product":"Red Hat Enterprise Linux 9","packageName":"rhel8/flatpak-sdk","defaultStatus":"unaffected","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/o:redhat:enterprise_linux:9"]},{"vendor":"Red Hat","product":"Red Hat Enterprise Linux 9","packageName":"util-linux","defaultStatus":"unaffected","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/o:redhat:enterprise_linux:9"]},{"vendor":"Red Hat","product":"Red Hat OpenShift Container Platform 4","packageName":"openshift/ose-rhel-coreos-8","defaultStatus":"unaffected","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/a:redhat:openshift:4"]},{"vendor":"Red Hat","product":"Red Hat OpenShift Container Platform 4","packageName":"openshift/ose-rhel-coreos-9","defaultStatus":"unaffected","collectionURL":"https://access.redhat.com/downloads/content/package-browser/","cpes":["cpe:/a:redhat:openshift:4"]}],"references":[{"url":"https://access.redhat.com/errata/RHSA-2026:63162","name":"RHSA-2026:63162","tags":["vendor-advisory","x_refsource_REDHAT"]},{"url":"https://access.redhat.com/security/cve/CVE-2026-78409","tags":["vdb-entry","x_refsource_REDHAT"]},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2522607","name":"RHBZ#2522607","tags":["issue-tracking","x_refsource_REDHAT"]},{"url":"https://github.com/util-linux/util-linux/security/advisories/GHSA-8f2p-47x3-43mv"}],"metrics":[{"other":{"content":{"value":"Important","namespace":"https://access.redhat.com/security/updates/classification/"},"type":"Red Hat severity rating"}},{"cvssV3_1":{"attackComplexity":"HIGH","attackVector":"LOCAL","availabilityImpact":"HIGH","baseScore":7,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"LOW","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","version":"3.1"},"format":"CVSS"}],"problemTypes":[{"descriptions":[{"cweId":"CWE-59","description":"Improper Link Resolution Before File Access ('Link Following')","lang":"en","type":"CWE"}]}],"providerMetadata":{"shortName":"redhat","orgId":"53f830b8-0a3f-465b-8143-3b8a9948e749","dateUpdated":"2026-10-21T17:51:49.053Z"},"datePublic":"2026-09-02T00:00:00.000Z","x_redhatCweChain":"CWE-59: Improper Link Resolution Before File Access ('Link Following')","workarounds":[{"lang":"en","value":"Upgrade to util-linux v2.41.6, v2.42.3, or later. Until a fix is applied, do not allow unprivileged /etc/fstab entries that specify X-mount.subdir."}],"timeline":[{"lang":"en","time":"2026-06-17T00:00:00.000Z","value":"Reported to Red Hat."},{"lang":"en","time":"2026-09-02T00:00:00.000Z","value":"Made public."}],"credits":[{"lang":"en","value":"Upstream acknowledges Zhuorao Yang (Huawei Cloud) as the original reporter."}],"x_generator":{"engine":"cvelib 1.8.0"}},"adp":[{"title":"CISA ADP Vulnrichment","references":[{"url":"https://github.com/util-linux/util-linux/security/advisories/GHSA-8f2p-47x3-43mv","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-09-02T15:29:06.011028Z","id":"CVE-2026-78409","options":[{"Exploitation":"poc"},{"Automatable":"no"},{"Technical Impact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-09-02T15:31:33.985Z"}}]}}}