Summary
ewen-lbh/ffcss Late-Unicode normalization vulnerability
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 [-_ .].
// lookupPreprocess applies transformations to s so that it can be compared
// to search for something.
// For example, it is used by (ThemeStore).Lookup
func lookupPreprocess(s string) string {
return strings.ToLower(norm.NFKD.String(regexp.MustCompile(`[-_ .]`).ReplaceAllString(s, "")))
}
Take the following equivalent Unicode character U+2024 (․). Initially, the lookupPreprocess() function would compile the regex and replace the regular dot (.). However, the U+2024 (․) would bypass the ReplaceAllString(). When the normalization operation is applied to U+2024 (․), the resulting character will be U+002E (.). Thus, the dot was reintroduced back.
References
Impact
The lookupPreprocess() can be easily bypassed with equivalent Unicode characters like U+FE4D (﹍), which would result in the omitted U+005F (_), for instance. It should be noted here that the variable s is user-controlled data coming from /cmd/ffcss/commands.go#L22-L28 the command args. 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.
CVE-2023-52081 has a CVSS score of 5.3 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.2.0); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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A simple fix would be to initially perform the Unicode normalization and then the rest of validations.
Frequently Asked Questions
- What is CVE-2023-52081? CVE-2023-52081 is a medium-severity security vulnerability in github.com/ewen-lbh/ffcss (go), affecting versions < 0.2.0. It is fixed in 0.2.0.
- How severe is CVE-2023-52081? CVE-2023-52081 has a CVSS score of 5.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of github.com/ewen-lbh/ffcss are affected by CVE-2023-52081? github.com/ewen-lbh/ffcss (go) versions < 0.2.0 is affected.
- Is there a fix for CVE-2023-52081? Yes. CVE-2023-52081 is fixed in 0.2.0. Upgrade to this version or later.
- Is CVE-2023-52081 exploitable, and should I be worried? Whether CVE-2023-52081 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2023-52081 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2023-52081? Upgrade
github.com/ewen-lbh/ffcssto 0.2.0 or later.