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…
Severity = CVSS. Probability = EPSS (FIRST). Exploitation = public signals: KEV, EUVD, ransomware, EPSS above 10 %, no account required.
Exploitation probability EPSS · FIRST
Exploitation signals 3 / 5
- KEV catalog (CISA)20 Oct 2022
- Exploited in EUVD (ENISA)20 Oct 2022
- Used by ransomwareno
- EPSS above 10 %49.2%
- No account, over the networkno
What to do
Fix
Update to a fixed version: 5.10.38-1
CISA guidance: Apply updates per vendor instructions.
Meanwhile
Take the service off the internet or restrict access to it, watch the logs and look for signs of compromise.
Manufacturers (CRA)
Exploited vulnerability in your product: early warning to ENISA within 24 h, then notification within 72 h (Article 14 of the Cyber Resilience Act). The CRA explained
Description ENISA EUVD
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.
Affected products
- 5.4 kernel <5.4.0-72.80
- 4.4 kernel <4.4.0-209.241
- 5.8 kernel <5.8.0-50.56
- 4.15 kernel <4.15.0-142.146
Open source packages OSV
- linuxDebian:12 · CVE-2021-3493fixed in 5.10.38-1
- linuxDebian:13 · CVE-2021-3493fixed in 5.10.38-1
Timeline
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Published
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Exploitation reported (ENISA)
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Added to the KEV catalog
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CISA remediation due date
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EPSS peak: 49.2%
References
Other exploited vulnerabilities from the same vendor
- CVE-2026-46300Linux Kernel Missing Initialization of a Variable Vulnerability5.4 · Rising fast
- CVE-2026-53266Linux Kernel Out-of-Bounds Write Vulnerability4.7 · Actively exploited
- CVE-2025-39964Linux Kernel Race Condition Vulnerability4.4 · Actively exploited
- CVE-2025-39682Linux Kernel Improper Check for Unusual or Exceptional Conditions Vulnerability5.8 · Actively exploited
- CVE-2026-53362Linux Kernel Unspecified Vulnerability4.3 · Actively exploited
- CVE-2022-0995Linux Kernel Out-of-Bounds Write Vulnerability4.6 · Actively exploited