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Fencer Intel
high 7.1

CVE-2019-15794 json

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

published 6y ago modified 4mo ago also EUVD-2019-6717

cvss
7.1
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.2%
EPSS 1.2% chance of exploitation in 30 days, percentile 67%
public exploits
1
Exploit-DB

Summary

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.

Patch / fix

  • Ubuntu Linux kernel 5.0.0-37.40, 5.3.0-24.26
  • linux Debian 14, Debian 13, Debian 12 5.16.7-1

debian advisories DEBIAN-CVE-2019-15794

  • linux-gcp Ubuntu 18.04 LTS 5.0.0-1026.27~18.04.1
  • linux-hwe Ubuntu 18.04 LTS 5.0.0-37.40~18.04.1
  • linux-azure Ubuntu 18.04 LTS 5.0.0-1027.29~18.04.1
  • linux-aws-5.0 Ubuntu 18.04 LTS 5.0.0-1022.25~18.04.1
  • linux-gcp-5.3 Ubuntu 18.04 LTS 5.3.0-1009.10~18.04.1
  • linux-gke-5.0 Ubuntu 18.04 LTS 5.0.0-1026.27~18.04.2
  • linux-oem-osp1 Ubuntu 18.04 LTS 5.0.0-1030.34
  • linux-azure-5.3 Ubuntu 18.04 LTS 5.3.0-1008.9~18.04.1

ubuntu advisories UBUNTU-CVE-2019-15794

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel RHEL 8 4.18.0-348.el8
  • perf RHEL 8 4.18.0-348.el8
  • bpftool RHEL 8 4.18.0-348.el8
  • kernel-core RHEL 8 4.18.0-348.el8
  • kernel-tools RHEL 8 4.18.0-348.el8
  • python3-perf RHEL 8 4.18.0-348.el8
  • kernel-modules RHEL 8 4.18.0-348.el8
  • kernel-zfcpdump RHEL 8 4.18.0-348.el8

red hat advisories RHSA-2021:4356

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2019-15794 updated cvss 6.7

kernel: Overlayfs in the Linux kernel and shiftfs not restoring original value on error leading to a refcount underflow

  • Red Hat Enterprise Linux 8 kernel-rt, kernel-rt-kvm, kernel-rt-core, kernel-rt-modules, kernel-rt-debug-kvm, kernel-rt-debug-core, +6 more
    affected: workaround, no fix available
  • Red Hat CodeReady Linux Builder (v. 8) kernel-debuginfo-common-x86_64 4.18.0-348.el8, kernel-debuginfo-common-aarch64 4.18.0-348.el8, kernel-debuginfo-common-ppc64le 4.18.0-348.el8 Red Hat Enterprise Linux BaseOS (v. 8) perf 4.18.0-348.el8, kernel 4.18.0-348.el8, bpftool 4.18.0-348.el8, kernel-core 4.18.0-348.el8, kernel-tools 4.18.0-348.el8, python3-perf 4.18.0-348.el8, +15 more
    fixed: vendor fix RHSA-2021:4356
  • Red Hat Enterprise Linux 5 kernel Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, kernel-alt, python-perf, +9 more Red Hat Enterprise MRG 2 kernel-rt, mrg-rt-release, kernel-rt-trace, kernel-rt-vanilla, kernel-rt-firmware
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Timeline

  1. First public exploit (EDB-47692)
  2. Published

Exploit prediction

1.16% chance of exploitation in the next 30 days, higher than 67% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • EDB-47692 Ubuntu 19.10 - ubuntu-aufs-modified mmap_region() Breaks Refcounting in overlayfs/shiftfs Error Path dos, 2019-11-20

CVSS scores

assigned by version score vector
CNA 3.1 7.1 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H
NVD 3.1 6.7 CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.2 AV:L/AC:L/Au:N/C:C/I:C/A:C

Affected products

  • Ubuntu Linux kernel

Classification

Weakness
  • CWE-672 Operation on a Resource after Expiration or Release
Technology feeds

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.