CVE-2023-52081 – github.com/ewen-lbh/ffcss

Package

Manager: go
Name: github.com/ewen-lbh/ffcss
Vulnerable Version: >=0 <0.2.0

Severity

Level: Medium

CVSS v3.1: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

EPSS: 0.00131 pctl0.33399

Details

ewen-lbh/ffcss Late-Unicode normalization vulnerability ### Summary 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 `[-_ .]`. ```go // 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. ### 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](https://github.com/ewen-lbh/ffcss/blob/master/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. ### Remediation A simple fix would be to initially perform the Unicode normalization and then the rest of validations. ### References - https://sim4n6.beehiiv.com/p/unicode-characters-bypass-security-checks

Metadata

Created: 2023-12-28T21:16:57Z
Modified: 2024-03-01T14:35:42Z
Source: https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2023/12/GHSA-wpmx-564x-h2mh/GHSA-wpmx-564x-h2mh.json
CWE IDs: ["CWE-176", "CWE-74"]
Alternative ID: GHSA-wpmx-564x-h2mh
Finding: F184
Auto approve: 1