CVE-2022-4170: The rxvt-unicode package is vulnerable to a remote code execution, in the Perl background extension, when an a

This week

CRITICAL 9.8REMOTEWATCHLISTDOWNGRADEDOWNGRADEMITIGATE

CVE-2022-4170 is a critical-severity flaw (CVSS 9.8) affecting rxvt-unicode, extra packages for enterprise linux, fedora. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The rxvt-unicode package is vulnerable to a remote code execution, in the Perl background extension, when an attacker can control the data written to the user's terminal and certain options are set.

Why this priority

Critical severity
Remotely exploitable, no login, no user action
On your watchlist

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

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	2.2% (top 17%)
CISA exploited list	No
Weakness	CWE-74
Published	2022-12-09
Last modified	2026-06-17

Publisher (CNA): Fedora Project · Vendor: fedoraproject · rxvt-unicode project

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

Am I affected?

Timeline

2022-12-09 18:15 UTCPublished CVE record published
2026-06-17 05:20 UTCUpdated Record last modified

rxvt-unicode project rxvt-unicode DOWNGRADE

Affected: 9.25 · 9.26

Fixed in: no fixed release known

Safe to downgrade to: a release before 9.25

1. Check installed version

apt-cache policy rxvt-unicode || rpm -q rxvt-unicode || rxvt-unicode --version

2. No fixed release: DOWNGRADE to a release before 9.25 (Debian / Ubuntu)

apt-cache madison rxvt-unicode sudo apt install rxvt-unicode=<VERSION_BEFORE_9.25> sudo apt-mark hold rxvt-unicode

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

dnf --showduplicates list rxvt-unicode sudo dnf downgrade rxvt-unicode-<VERSION_BEFORE_9.25> sudo dnf versionlock add rxvt-unicode

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.

fedoraproject extra packages for enterprise linux DOWNGRADE

Affected: 8.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 8.0

1. Check installed version

apt-cache policy extra-packages-for-enterprise-linux || rpm -q extra-packages-for-enterprise-linux || extra-packages-for-enterprise-linux --version

2. No fixed release: DOWNGRADE to a release before 8.0 (Debian / Ubuntu)

apt-cache madison extra-packages-for-enterprise-linux sudo apt install extra-packages-for-enterprise-linux=<VERSION_BEFORE_8.0> sudo apt-mark hold extra-packages-for-enterprise-linux

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

dnf --showduplicates list extra-packages-for-enterprise-linux sudo dnf downgrade extra-packages-for-enterprise-linux-<VERSION_BEFORE_8.0> sudo dnf versionlock add extra-packages-for-enterprise-linux

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.

fedoraproject fedora MITIGATE

Affected: 37

Fixed in: no fixed release known

Safe to downgrade to: a release before 37

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.

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-2022-4170?

rxvt-unicode: downgrade or apply the listed mitigation; extra packages for enterprise linux: downgrade or apply the listed mitigation; fedora: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2022-4170 being exploited?

CVE-2022-4170 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-2022-4170 affect?

CVE-2022-4170 affects rxvt-unicode, extra packages for enterprise linux, fedora. Severity is critical (CVSS 9.8). The rxvt-unicode package is vulnerable to a remote code execution, in the Perl background extension, when an attacker can control the data written to the user's terminal and certain options are set.

How urgent is CVE-2022-4170?

Priority 65/100. Critical severity; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Perl vulnerabilities

Related CVEs

CVE-2021-33477 HIGH 8.8 DOWNGRADE DOWNGRADE rxvt-unicode 9.22, rxvt 2.7.10, mrxvt 0.5.4, and Eterm 0.9.7 allow (potentially remote) code execution because

References

← Back to latest CVEs