CVE-2019-15794 - CVE House
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Status published High CVE-2019-15794

Reference counting error in overlayfs/shiftfs error path when used in conjuction with aufs

Vulnerability 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.

Impact Analysis

Refer to official advisory for detailed impact metrics.

Remediation

Ensure systems are updated to the latest vendor-supplied patch levels.

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Credits & Attribution

The following person or organization is credited with identifying this vulnerability, as recorded in the NVD database:

  • Jann Horn of Google Project Zero

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Affected Vendor

Affected Software

Linux kernel
Vulnerable Versions:
5.3 kernel, 5.0 kernel

Timeline

Official Publish: April 23rd, 2020
Last Modified: September 16th, 2024
Added to House: July 20th, 2026

CVSS Vectors

V3: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H

Weaknesses (CWE)

CWE-672

MITRE ATT&CK TTPs

No associated TTPs found for this vulnerability.