CVE-2021-3493

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Summary

CVECVE-2021-3493
StatePUBLIC
Assigner[email protected]
Source PriorityCVE Program / NVD first with legacy fallback
Published2021-04-17 05:15:00 UTC
Updated2023-07-07 19:10:00 UTC
DescriptionThe 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.

Risk And Classification

EPSS: 0.771920000 probability, percentile 0.989620000 (date 2026-04-01)

CISA KEV: Listed on 2022-10-20; due 2022-11-10; ransomware use Unknown

Problem Types: CWE-863

CISA Known Exploited Vulnerability

VendorLinux
ProductKernel
NameLinux Kernel Privilege Escalation Vulnerability
Required ActionApply updates per vendor instructions.
Noteshttps://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7c03e2cda4a584cadc398e8f6641ca9988a39d52; https://nvd.nist.gov/vuln/detail/CVE-2021-3493

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Canonical Ubuntu Linux All All All All
Operating System Canonical Ubuntu Linux All All All All

References

ReferenceSourceLinkTags
Ubuntu Overlayfs Local Privilege Escalation ≈ Packet Storm MISC packetstormsecurity.com
oss-security - [CVE-2021-3493] Ubuntu Linux kernel overlayfs fs caps privilege escalation MISC www.openwall.com
kernel/git/torvalds/linux.git - Linux kernel source tree MISC git.kernel.org
Ubuntu OverlayFS Local Privilege Escalation ≈ Packet Storm MISC packetstormsecurity.com
Kernel Live Patch Security Notice LSN-0076-1 ≈ Packet Storm MISC packetstormsecurity.com
USN-4917-1: Linux kernel vulnerabilities | Ubuntu security notices | Ubuntu MISC ubuntu.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis
CISA Known Exploited Vulnerabilities catalog CISA www.cisa.gov kev

Vendor Comments And Credit

Discovery Credit

LEGACY: An independent security researcher reporting to the SSD Secure Disclosure program

Legacy QID Mappings

  • 180539 Debian Security Update for linux (CVE-2021-3493)
  • 198331 Ubuntu Security Notification for Linux kernel (OEM) vulnerabilities (USN-4915-1)
  • 198332 Ubuntu Security Notification for Linux kernel vulnerabilities (USN-4916-1)
  • 198333 Ubuntu Security Notification for Linux kernel vulnerabilities (USN-4917-1)
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