CVE-2023-52081: ffcss is a CLI interface to apply and configure Firefox CSS themes

Q: How do I fix CVE-2023-52081?

firefox css: upgrade to 0.2.0. Exact commands for each OS are on this page.

Q: Is CVE-2023-52081 being exploited?

CVE-2023-52081 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2023-52081 affect?

CVE-2023-52081 affects firefox css. Severity is medium (CVSS 5.3). ffcss is a CLI interface to apply and configure Firefox CSS themes. Prior to 0.2.0, the function `lookupPreprocess()` is meant to apply some transformations to a string by disabling characters in the regex `[-_ .]`. However, due to the use

Q: How urgent is CVE-2023-52081?

Priority 40/100. Public exploit reference; Remotely exploitable, no login, no user action

This week

MEDIUM 5.3REMOTEUPGRADE

CVE-2023-52081 is a medium-severity flaw (CVSS 5.3) affecting firefox css. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

ffcss is a CLI interface to apply and configure Firefox CSS themes. Prior to 0.2.0, the function `lookupPreprocess()` is meant to apply some transformations to a string by disabling characters in the regex `[-_ .]`. However, due to the use of late Unicode normalization of type NFKD, it is possible to bypass that validation and re-introduce all the characters in the regex `[-_ .]`. The `lookupPreprocess()` can be easily bypassed with equivalent Un

Why this priority

Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.5% (top 56%)
CISA exploited list	No
Weakness	CWE-74, CWE-176
Published	2023-12-28
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: ewen-lbh

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

Am I affected?

Timeline

2023-12-28 16:16 UTCPublished CVE record published
2026-06-17 06:42 UTCUpdated Record last modified

ewen-lbh firefox css UPGRADE

Affected: < 0.2.0

Fixed in: 0.2.0

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy firefox-css || rpm -q firefox-css || firefox-css --version

2. UPGRADE to 0.2.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade firefox-css

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade firefox-css

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

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-2023-52081?

firefox css: upgrade to 0.2.0. Exact commands for each OS are on this page.

Is CVE-2023-52081 being exploited?

CVE-2023-52081 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-2023-52081 affect?

CVE-2023-52081 affects firefox css. Severity is medium (CVSS 5.3). ffcss is a CLI interface to apply and configure Firefox CSS themes. Prior to 0.2.0, the function `lookupPreprocess()` is meant to apply some transformations to a string by disabling characters in the regex `[-_ .]`. However, due to the use

How urgent is CVE-2023-52081?

Priority 40/100. Public exploit reference; Remotely exploitable, no login, no user action

Software pages

Mozilla Firefox vulnerabilities

References

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