CVE-2019-15791Public exploit

System crash via unreferenced lower-file descriptor

Published Apr 23, 2020 · Updated Sep 17, 2024

Reference-count underflow in Ubuntu Kernel 5.0 and 5.3 series allows local users to crash the system through a crafted Btrfs ioctl. The shiftfs_btrfs_ioctl_fd_replace() path installs an fd for a lower-filesystem file without acquiring the additional reference that fd_install() consumes, leaving a dangling file reference after the ioctl closes it. Unprivileged user namespaces expose this path in a default Ubuntu 19.10 installation; the demonstrated outcome is a kernel crash, while Canonical also identifies arbitrary code execution as an impact.

CVSS severity7.1
High
EPSS probability1.32%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Reference-count underflow in Ubuntu Kernel 5.0 and 5.3 series allows local users to crash the system through a crafted Btrfs ioctl. The shiftfs_btrfs_ioctl_fd_replace() path installs an fd for a lower-filesystem file without acquiring the additional reference that fd_install() consumes, leaving a dangling file reference after the ioctl closes it. Unprivileged user namespaces expose this path in a default Ubuntu 19.10 installation; the demonstrated outcome is a kernel crash, while Canonical also identifies arbitrary code execution as an impact.

The record

CVE
CVE-2019-15791
Published
Apr 23, 2020
Updated
Sep 17, 2024
Vendor
Canonical
Product
Ubuntu Kernel
Classifications
CWE-672, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 23, 2020CVE publishedPublication date reported by the CVE source.
  2. Sep 17, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=5.0 kernel <5.0.0-35.38
  2. Affected versionversion=5.3.0-11.12 <5.3 kernel* changes=[{"at":"5.3.0-22.24","status":"unaffected"}]

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Canonical · Ubuntu Kernelversion=5.0 kernel <5.0.0-35.38; version=5.3.0-11.12 <5.3 kernel* changes=[{"at":"5.3.0-22.24","status":"unaffected"}]

Published CVSS scores

7.1Canonical CNACVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H
7.8Ubuntu Security TeamCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-672Operation on a Resource after Expiration or Release
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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