GHSA-WPMX-564X-H2MH
Vulnerability from github – Published: 2023-12-28 21:16 – Updated: 2024-03-01 14:35Summary
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.
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.
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
{
"affected": [
{
"package": {
"ecosystem": "Go",
"name": "github.com/ewen-lbh/ffcss"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "0.2.0"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2023-52081"
],
"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"
},
"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 (\u2024). Initially, the `lookupPreprocess()` function would compile the regex and replace the regular dot (.). However, the U+2024 (\u2024) would bypass the `ReplaceAllString()`. When the normalization operation is applied to U+2024 (\u2024), 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 (\ufe4d), 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",
"id": "GHSA-wpmx-564x-h2mh",
"modified": "2024-03-01T14:35:42Z",
"published": "2023-12-28T21:16:57Z",
"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"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N",
"type": "CVSS_V3"
}
],
"summary": "ewen-lbh/ffcss Late-Unicode normalization vulnerability"
}
Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.