CVE intelligence and bounded remediation
CVE-2021-3493 — Linux Kernel Privilege Escalation Vulnerability
The overlayfs implementation in the linux kernel did not properly validate with respect to user namespaces the setting of file capabilities on files in an underlying file system. Due to the combination of unprivileged user namespaces along with a patch carried in the Ubuntu kernel to allow unprivileged overlay mounts, an attacker could use this to gain elevated privileges.
- Severity
- High
- CVSS
- 8.8 (3.1)
- Published
- 2021-04-17
- CISA KEV
- Known exploited
- Ecosystem
- operating-system
- Weaknesses
- CWE-270, CWE-863
Affected products
- canonical / ubuntu_linux
Showing 1 representative product identities from 3 source matches. Confirm exact affected versions with the linked vendor and NVD evidence.
Matched remediation archetype
Privilege escalation and unsafe privilege management
This catalog composition supplies bounded fallback guidance. Explicitly reviewed curated workflows load with the complete record below.
Check exposure
- Map service accounts, operating-system identities, roles, capabilities, impersonation, set-user transitions, and administrative helper paths.
- Determine whether untrusted users or lower-privilege processes can reach the affected transition or modify inputs it trusts.
- Review file, socket, registry, device, job, container, and cloud-role permissions used before and after privilege changes.
Remediate safely
- Apply the supported fix and redesign privileged operations as a minimal, authenticated, allowlisted interface.
- Drop privileges before processing untrusted input, verify the drop succeeds, and remove unnecessary roles, capabilities, and write permissions.
- Validate ownership and permissions at time of use and add explicit lower-to-higher privilege boundary tests.
Authoritative sources
Complete CVE record and remediation plan
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