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CVE-2019-15794

7.1 · HIGH

Overlayfs in the Linux kernel and shiftfs, a non-upstream patch to the Linux kernel included in the Ubuntu 5.0 and 5.3 kernel series, both replace vma->vm_file in their mmap handlers.

Published Apr 24, 2020CWE-672EPSS 1.16%

Overview

CVE-2019-15794 is a high-severity vulnerability. It was published on April 24, 2020 and has a CVSS 3.1 base score of 7.1 (HIGH).

This vulnerability has a CVSS 3.1 base score of 7.1, rated HIGH. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

Technical description

Overlayfs in the Linux kernel and shiftfs, a non-upstream patch to the Linux kernel included in the Ubuntu 5.0 and 5.3 kernel series, both replace vma->vm_file in their mmap handlers. On error the original value is not restored, and the reference is put for the file to which vm_file points. On upstream kernels this is not an issue, as no callers dereference vm_file following after call_mmap() returns an error. However, the aufs patchs change mmap_region() to replace the fput() using a local variable with vma_fput(), which will fput() vm_file, leading to a refcount underflow.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refgit.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/eoan/commit/?id=270d16ae48a4dbf1c7e25e94cc3e38b4bea37635Refgit.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/eoan/commit/?id=ef81780548d20a786cc77ed4203fca146fd81ce3Refusn.ubuntu.com/usn/usn-4208-1Refusn.ubuntu.com/usn/usn-4209-1Refgit.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/eoan/commit/?id=270d16ae48a4dbf1c7e25e94cc3e38b4bea37635Refgit.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/eoan/commit/?id=ef81780548d20a786cc77ed4203fca146fd81ce3Refusn.ubuntu.com/usn/usn-4208-1Refusn.ubuntu.com/usn/usn-4209-1

How CyberStrike helps

Frequently asked questions

What is CVE-2019-15794?

CVE-2019-15794 is a high-severity vulnerability. It was published on April 24, 2020 and has a CVSS 3.1 base score of 7.1 (HIGH).

How severe is CVE-2019-15794?

This vulnerability has a CVSS 3.1 base score of 7.1, rated HIGH. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2019-15794?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2019-15794?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2019-15794 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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