ghsa-wpmx-564x-h2mh
Vulnerability from github
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 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 seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.