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{"schema_version":"1.9.0","id":"GHSA-wpmx-564x-h2mh","published":"2023-12-28T21:16:57Z","modified":"2026-09-10T03:50:09.240545301Z","aliases":["CVE-2023-52081","GO-2023-2426"],"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","affected":[{"package":{"name":"github.com/ewen-lbh/ffcss","ecosystem":"Go","purl":"pkg:golang/github.com/ewen-lbh/ffcss"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"0.2.0"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2023/12/GHSA-wpmx-564x-h2mh/GHSA-wpmx-564x-h2mh.json"}}],"references":[{"type":"WEB","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":"WEB","url":"https://github.com/ewen-lbh/ffcss/commit/f9c491874b858a32fcae15045f169fd7d02f90dc"},{"type":"PACKAGE","url":"https://github.com/ewen-lbh/ffcss"}],"database_specific":{"cwe_ids":["CWE-176","CWE-74"],"github_reviewed":true,"github_reviewed_at":"2023-12-28T21:16:57Z","nvd_published_at":"2023-12-28T16:16:02Z","severity":"MODERATE"},"severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"}]} |