dbcve.org
FedoraOperating system · Fedoraproject

CVE-2022-4170

CRITICAL · 9.8 CVSS v3.1 Published 2022-12-09
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

The rxvt-unicode (urxvt) terminal emulator contains a remote code execution vulnerability in its Perl background extension. When certain options are enabled and an attacker can control data written to the victim's terminal (e.g., via malicious output, paste events, or untrusted content), the Perl extension improperly processes this data leading to arbitrary command execution.

MitigationDisable the Perl background extension in urxvt if not required, or ensure terminal output is not sourced from untrusted sources. Users should avoid rendering potentially malicious content in their terminal until a patch is applied.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
FedoraOperating system
Affected:= 37
Rxvt UnicodeApplication
Affected:= 9.25= 9.26
Extra Packages For Enterprise LinuxApplication
Affected:= 8.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Verify urxvt installation
    Check if rxvt-unicode or urxvt is installed on the system using the package manager (e.g., rpm -qa | grep -i urxvt, dpkg -l | grep urxvt, or which urxvt)
    Affected if urxvt is not installed on the system
  2. Identify installed version
    Query the installed package version using the system package manager (e.g., rpm -q rxvt-unicode, dpkg -s rxvt-unicode) and compare against the affected versions 9.25 and 9.26, as well as Fedora 37 and EPEL 8.0
    Affected if The installed version matches 9.25, 9.26, or is from Fedora 37 or EPEL 8.0
  3. Locate Perl extension configuration
    Examine the urxvt configuration files in the user's home directory (~/.Xresources, ~/.Xdefaults) and system-wide (/etc/X11/app-defaults/Urxvt*) for any references to the background Perl extension
    Affected if The background extension is explicitly loaded or referenced in configuration files
  4. Check for background extension in perl lib path
    Look for the background.pm Perl module in the urxvt perl library directory (typically /usr/lib/urxvt/perl/ or /usr/share/urxvt/perl/)
    Affected if The background.pm Perl extension file exists in the urxvt perl library directory and is accessible to user sessions

A user is affected if urxvt is installed with version 9.25 or 9.26 (or from Fedora 37/EPEL 8.0) AND the Perl background extension is enabled in the configuration or present in the perl library path.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Disable the Perl background extension in urxvt if not required, or ensure terminal output is not sourced from untrusted sources. Users should avoid rendering potentially malicious content in their terminal until a patch is applied.

Recommended fix Moderate confidence

rxvt-unicode version 9.27 or later

  1. 1. Identify the rxvt-unicode (urxvt) package installation on your system
  2. 2. Update the package repository metadata
  3. 3. Upgrade rxvt-unicode to version 9.27 or later (the first fixed release)
  4. 4. Verify the installed version matches or exceeds the fixed release
  5. 5. Restart any running urxvt instances to ensure the updated binaries are in use
Caveat Minor: Upgrading terminal emulators may reset custom configuration preferences; backup any custom ~/.Xresources or urxvt Perl extension configurations before upgrade

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Fedora Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
Get help mitigating

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $6,176.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2022-4170 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2022-4170 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data