CVE-2023-2640

Public Exploit

Description

On Ubuntu kernels carrying both c914c0e27eb0 and "UBUNTU: SAUCE: overlayfs: Skip permission checking for trusted.overlayfs.* xattrs", an unprivileged user may set privileged extended attributes on the mounted files, leading them to be set on the upper files without the appropriate security checks.

Remediation

Workaround:

  • If not needed, disable the ability for unprivileged users to create namespaces. To do this temporarily, do: sudo sysctl -w kernel.unprivileged_userns_clone=0 To disable across reboots, do: echo kernel.unprivileged_userns_clone=0 | \ sudo tee /etc/sysctl.d/99-disable-unpriv-userns.conf

Category

7.8
CVSS
Severity: High
CVSS 3.1 •
EPSS 91.87% Top 5%
Vendor Advisory ubuntu.com
Affected: Canonical Ubuntu Kernel
Published at:
Updated at:

References

Link Tags
https://ubuntu.com/security/notices/USN-6250-1 vendor advisory
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-2640 third party advisory issue tracking
https://wiz.io/blog/ubuntu-overlayfs-vulnerability mitigation third party advisory exploit technical description
https://lists.ubuntu.com/archives/kernel-team/2023-July/140923.html patch mailing list

Frequently Asked Questions

What is the severity of CVE-2023-2640?
CVE-2023-2640 has been scored as a high severity vulnerability.
How to fix CVE-2023-2640?
As a workaround for remediating CVE-2023-2640: If not needed, disable the ability for unprivileged users to create namespaces. To do this temporarily, do: sudo sysctl -w kernel.unprivileged_userns_clone=0 To disable across reboots, do: echo kernel.unprivileged_userns_clone=0 | \ sudo tee /etc/sysctl.d/99-disable-unpriv-userns.conf
Is CVE-2023-2640 being actively exploited in the wild?
It is possible that CVE-2023-2640 is being exploited or will be exploited in a near future based on public information. According to its EPSS score, there is a ~92% probability that this vulnerability will be exploited by malicious actors in the next 30 days.
What software or system is affected by CVE-2023-2640?
CVE-2023-2640 affects Canonical Ubuntu Kernel.
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