Open edX Platform CVE-2026-85272

Requires an authenticated course author or staff user holding course-import permission in Open edX Studio (CMS), on a version from Aspen.1 up to but not including Ulmo/Verawood.1. The attacker must submit a crafted .tar.gz (gzip tar) archive through the import_olx flow (cms.djangoapps.contentstore.views.import_export.import_handler); the malicious member must use a path that extends the target staging directory's base64 name as a string prefix so _is_bad_path's startswith check is bypassed. Exploitation is meaningfully limited to multi-tenant deployments where a vulnerable sibling course staging directory sharing the prefix exists concurrently. Zip archives are NOT viable because ZipFile.extractall strips parent-traversal segments. Impact is confined to cross-tenant file corruption - no code execution, arbitrary read, or arbitrary write outside the sibling staging area.

This is a genuine but low-severity issue whose real-world priority is modest. The vendor CVSS 3.1 vector (AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N = 4.3 Medium) is well-calibrated to the described flaw: a segment-unaware startswith containment check lets a crafted tar.gz member escape into a sibling course staging directory sharing a base64 name prefix, but the advisory explicitly disclaims arbitrary filesystem writes, arbitrary reads, and code execution - impact is limited cross-tenant file corruption (integrity-only, I:L). PR:L is the critical limiter: exploitation requires an authenticated course author or staff user who already holds course-import permission, so this is an insider/tenant-abuse or compromised-privileged-account scenario, not open remote exploitation. No EPSS score, no CISA KEV listing, and no public exploit are present in the provided data (no public exploit identified at time of analysis), consistent with a recently-disclosed, hard-to-monetize integrity bug. The 'RCE' tag conflicts directly with the advisory text, which affirmatively rules out code execution - treat the tag as mislabeled, not as evidence of higher impact. Net: real, patch it in normal cadence, but not an emergency.

An authenticated course author or staff user with course-import rights on a multi-tenant Open edX instance uploads a crafted .tar.gz through the Studio (CMS) import_olx flow containing a member path like ../<base64prefix>evil/sentinel.txt. Because _is_bad_path compares resolved path strings with startswith rather than by path component, the entry escapes its own staging directory into a sibling course's staging directory that shares the base64 name prefix, corrupting or overwriting files belonging to another tenant. No public exploit code is identified at time of analysis; the fix commits include end-to-end tests demonstrating the prefix-bypass technique.