title: Mishandling of file-system uid/gid with namespaces in shiftfs
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.
problem types: CWE-538 File and Directory Information Exposure
affected:
{
product: Shiftfs in the Linux kernel
vendor: Ubuntu
versions:
changes: [at: 5.3.0-22.24, status: unaffected], lessThan: 5.3 kernel*, status: affected, version: 5.3.0-11.12, versionType: custom
lessThan: 5.0.0-35.38, status: affected, version: 5.0 kernel, versionType: custom
}
metrics:
cvssV3_1: [
attackComplexity: LOW
attackVector: LOCAL
availabilityImpact: NONE
baseScore: 6.5
baseSeverity: MEDIUM
confidentialityImpact: HIGH
integrityImpact: NONE
privilegesRequired: LOW
scope: CHANGED
userInteraction: NONE
vectorString: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N
version: 3.1
]