High [CVE-2026-87766] symlink traversal via /oldroot allows writing files outside sandbox during setup
This high-severity Red Hat Linux advisory covers CVE-2026-87766 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9.
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Summary
A flaw was found in bubblewrap. During sandbox setup, creating files or directories under the new root can follow a parent symlink onto the host via /oldroot, writing attacker-chosen paths outside the sandbox as the launching user.
This happens before the sandboxed process starts. This issue is GHSA-pxhw-h44j-8pfx.
It is fixed in bubblewrap 0.12.0. This flaw in bubblewrap is rated as Important because it allows a local attacker to write files outside of a sandbox on the host system.
While the created files are written with the privileges of the user launching bubblewrap, this can lead to unintended file creation on the host filesystem. Red Hat severity: Important — CVSS 8.8 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H).
Weakness: CWE-59. Affected Red Hat products: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 8; Red Hat Enterprise Linux 9.
Red Hat lists Red Hat Hardened Images as not affected. Red Hat does not currently list a fixing RHSA for this CVE.
Affected products named by the advisory: Red Hat package: bubblewrap.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 2 hours ago·verify at source
Mitigation checklist
- Do not create files on untrusted content with unpatched bwrap. Do not install untrusted Flatpaks. No upstream fix for older setuid builds.
Official advisory · high-confidence parse· fetched 2 hours ago·verify at source
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