{"id":"CVE-2023-52081","aliases":["GHSA-wpmx-564x-h2mh","GO-2023-2426"],"url":"https://o3.security/vulnerability/CVE-2023-52081","summary":"ewen-lbh/ffcss late-Unicode normalization vulnerability","details":"### Summary\nThe 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 `[-_ .]`. \n\n```go\n// lookupPreprocess applies transformations to s so that it can be compared\n// to search for something.\n// For example, it is used by (ThemeStore).Lookup\nfunc lookupPreprocess(s string) string {\n\treturn strings.ToLower(norm.NFKD.String(regexp.MustCompile(`[-_ .]`).ReplaceAllString(s, \"\")))\n}\n``` \n\nTake 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.\n\n### Impact\n\nThe `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.\n\n### Remediation\n\nA simple fix would be to initially perform the Unicode normalization and then the rest of validations.\n\n### References\n\n - https://sim4n6.beehiiv.com/p/unicode-characters-bypass-security-checks\n","published":"2023-12-28T15:34:17.132Z","modified":"2026-08-27T03:57:01.846025864Z","cvss":{"score":5.3,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":1,"affectedPackages":[{"ecosystem":"Go","name":"github.com/ewen-lbh/ffcss","fixedVersion":"0.2.0"}],"fix":{"url":"https://github.com/ewen-lbh/ffcss/commit/f9c491874b858a32fcae15045f169fd7d02f90dc","label":"ewen-lbh/ffcss@f9c4918"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2023/52xxx/CVE-2023-52081.json"},{"type":"ADVISORY","url":"https://github.com/ewen-lbh/ffcss/security/advisories/GHSA-wpmx-564x-h2mh"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2023-52081"},{"type":"FIX","url":"https://github.com/ewen-lbh/ffcss/commit/f9c491874b858a32fcae15045f169fd7d02f90dc"},{"type":"PACKAGE","url":"https://github.com/ewen-lbh/ffcss"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-27T03:57:01.846025864Z"}}