CVE-2019-15793
Description
In shiftfs, a non-upstream patch to the Linux kernel included in the Ubuntu 5.0 and 5.3 kernel series, several locations which shift ids translate user/group ids before performing operations in the lower filesystem were translating them into init_user_ns, whereas they should have been translated into the s_user_ns for the lower filesystem. This resulted in using ids other than the intended ones in the lower fs, which likely did not map into the shifts s_user_ns. A local attacker could use this to possibly bypass discretionary access control permissions.
Predictions
Heuristic predictions, AS-IS, for prioritization only.
Mitigations
No mitigations published for this CVE yet.
The vendor-content worker queues fetches as references arrive (check back in a few minutes). Or — if you've already worked around this in production — publish your fix to the community-verified tier.
✚ Propose a mitigation on Community → Mitigations published via the community go through AI scoring + 2 human reviewers + 7-day silent objection window before landing here withsource_tier=community-verified.
Exploits
Public proof-of-concept code below. AS-IS, for defenders and authorised testing only.
Exploit-DB
Ubuntu 19.10 - Refcount Underflow and Type Confusion in shiftfs
OS impact
Debian Fixed 5 releases
| Version | Status | Fixed in |
|---|---|---|
| trixie | Fixed | 0 |
| sid | Fixed | 0 |
| forky | Fixed | 0 |
| bullseye | Fixed | 0 |
| bookworm | Fixed | 0 |
References
Community-verified mitigations for this CVE will appear above when contributors publish them.
Verify integrity in audit chain (admin only). AS-IS.