CVE-2021-4115: There is a flaw in polkit which can allow an unprivileged user to cause polkit to crash, due to process file d

This month

MEDIUM 5.5WATCHLISTDOWNGRADEMITIGATEMITIGATE

CVE-2021-4115 is a medium-severity flaw (CVSS 5.5) affecting polkit, enterprise linux, fedora. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

There is a flaw in polkit which can allow an unprivileged user to cause polkit to crash, due to process file descriptor exhaustion. The highest threat from this vulnerability is to availability. NOTE: Polkit process outage duration is tied to the failing process being reaped and a new one being spawned

Why this priority

Public exploit reference
On your watchlist

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	5.5 (Medium)
Attack vector	Local
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.5% (top 55%)
CISA exploited list	No
Weakness	CWE-400
Published	2022-02-21
Last modified	2026-06-17

Publisher (CNA): Red Hat, Inc. · Vendor: canonical · debian · fedoraproject · oracle · polkit project · redhat

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2022-02-21 22:15 UTCPublished CVE record published
2026-06-17 04:19 UTCUpdated Record last modified

polkit project polkit DOWNGRADE

Affected: 0.117

Fixed in: no fixed release known

Safe to downgrade to: a release before 0.117

1. Check installed version

apt-cache policy polkit || rpm -q polkit || polkit --version

2. No fixed release: DOWNGRADE to a release before 0.117 (Debian / Ubuntu)

apt-cache madison polkit sudo apt install polkit=<VERSION_BEFORE_0.117> sudo apt-mark hold polkit

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list polkit sudo dnf downgrade polkit-<VERSION_BEFORE_0.117> sudo dnf versionlock add polkit

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

redhat enterprise linux MITIGATE

Affected: 8.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 8.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

fedoraproject fedora MITIGATE

Affected: 34 · 35

Fixed in: no fixed release known

Safe to downgrade to: a release before 34

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

canonical ubuntu linux MITIGATE

Affected: 20.04 · 21.10

Fixed in: no fixed release known

Safe to downgrade to: a release before 20.04

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

debian debian linux MITIGATE

Affected: 11.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 11.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

oracle zfs storage appliance kit DOWNGRADE

Affected: 8.8

Fixed in: no fixed release known

Safe to downgrade to: a release before 8.8

1. Check installed version

apt-cache policy zfs-storage-appliance-kit || rpm -q zfs-storage-appliance-kit || zfs-storage-appliance-kit --version

2. No fixed release: DOWNGRADE to a release before 8.8 (Debian / Ubuntu)

apt-cache madison zfs-storage-appliance-kit sudo apt install zfs-storage-appliance-kit=<VERSION_BEFORE_8.8> sudo apt-mark hold zfs-storage-appliance-kit

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list zfs-storage-appliance-kit sudo dnf downgrade zfs-storage-appliance-kit-<VERSION_BEFORE_8.8> sudo dnf versionlock add zfs-storage-appliance-kit

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-4115?

polkit: downgrade or apply the listed mitigation; enterprise linux: mitigate or apply the listed mitigation; fedora: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-4115 being exploited?

CVE-2021-4115 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-4115 affect?

CVE-2021-4115 affects polkit, enterprise linux, fedora. Severity is medium (CVSS 5.5). There is a flaw in polkit which can allow an unprivileged user to cause polkit to crash, due to process file descriptor exhaustion. The highest threat from this vulnerability is to availability. NOTE: Polkit process outage duration is tied

How urgent is CVE-2021-4115?

Priority 40/100. Public exploit reference; On your watchlist

Software pages

Ubuntu vulnerabilities · Debian vulnerabilities

Related CVEs

CVE-2026-4897 MEDIUM 5.5 MITIGATE DOWNGRADE A flaw was found in polkit
CVE-2021-4034 HIGH 7.8 EXPLOITED UPGRADE DOWNGRADE Red Hat Polkit Out-of-Bounds Read and Write Vulnerability
CVE-2021-3560 HIGH 7.8 EXPLOITED UPGRADE MITIGATE Red Hat Polkit Incorrect Authorization Vulnerability

References

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