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Exploited vulnerability · CISA KEV

Is CVE-2021-3493 exploited? Yes: in CISA KEV since 20 Oct 2022

Gociux · Linux Kernel · data: CISA KEV, CVE record, FIRST EPSS

Yes. CVE-2021-3493, Linux Kernel Privilege Escalation Vulnerability, is being exploited in the wild. CISA added it to its Known Exploited Vulnerabilities catalog on 20 Oct 2022, 551 days after it was published. It affects Linux Kernel. If you run it, CISA's required action is: Apply updates per vendor instructions.

exploitedYesCISA KEV · 20 Oct 2022
ransomwareNot knownno confirmed use
EPSStop 5%very likely to be exploited
severity8.8CVSS 3.1 · high
US federal due10 Nov 2022BOD 22-01 deadline

What it is

The overlayfs stacking file system in Linux kernel does not properly validate the application of file capabilities against user namespaces, which could lead to privilege escalation.

VendorLinux (32 exploited CVEs in KEV)
ProductKernel
VulnerabilityLinux Kernel Privilege Escalation Vulnerability
WeaknessCWE-862
Published17 Apr 2021
Added to KEV20 Oct 2022
Reported by (CNA)canonical

What to do

  1. Check whether you run it. Look for Kernel in your asset inventory, including appliances and cloud images. Stack check lists every exploited Linux CVE at once.
  2. Apply the fix. Apply updates per vendor instructions.
  3. If you can't patch today, take the affected service off the internet or restrict who can reach it, and check its logs for signs of compromise since 17 Apr 2021.
  4. Get told next time. Email alerts when CISA adds a CVE for Linux.

Other exploited CVEs in Kernel

References

Questions

Is CVE-2021-3493 being exploited?

Yes. CISA added CVE-2021-3493 to the Known Exploited Vulnerabilities catalog on 20 Oct 2022, which means there is reliable evidence of exploitation in the wild.

Is CVE-2021-3493 used in ransomware attacks?

CISA does not list known ransomware use for it. That can change, and exploitation alone is reason to fix it first.

How do I fix CVE-2021-3493?

Apply updates per vendor instructions. Check Linux's advisory for the fixed versions, and if you can't patch quickly, restrict access to the affected Kernel and watch it for signs of compromise.

Sources: CISA KEV (exploitation, ransomware use, required action, due date), the CVE record (publication date, CVSS, CNA), NVD and FIRST EPSS (live score). More: all KEV additions in October 2022 · Linux scorecard · act-now radar.

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