CVE-2019-15793

Published: 12 November 2019

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.

From the Ubuntu Security Team

Jann Horn discovered that the shiftfs implementation in the Linux kernel did not use the correct file system uid/gid when the user namespace of a lower file system is not in the init user namespace. A local attacker could use this to possibly bypass DAC permissions or have some other unspecified impact.

Status

Severity score breakdown

References

• https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-15793
• https://ubuntu.com/security/notices/USN-4183-1
• https://ubuntu.com/security/notices/USN-4184-1
• NVD
• Launchpad
• Debian

Bugs

• https://bugs.launchpad.net/bugs/1850867