stoatchat before 0.15.5 Username Validation Bypass via Unicode Sanitization

{
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "cveMetadata": {
    "cveId": "CVE-2026-100674",
    "assignerOrgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10",
    "assignerShortName": "VulnCheck",
    "dateUpdated": "2026-09-26T13:23:37.620Z",
    "dateReserved": "2026-09-26T02:34:55.635Z",
    "datePublished": "2026-09-26T13:23:37.620Z",
    "state": "PUBLISHED"
  },
  "containers": {
    "cna": {
      "providerMetadata": {
        "orgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10",
        "shortName": "VulnCheck",
        "dateUpdated": "2026-09-26T13:23:37.620Z"
      },
      "datePublic": "2026-09-11T00:00:00.000Z",
      "title": "stoatchat before 0.15.5 Username Validation Bypass via Unicode Sanitization",
      "descriptions": [
        {
          "lang": "en",
          "value": "stoatchat before 0.15.5 fails to revalidate usernames after Unicode sanitization, allowing attackers to create usernames with forbidden characters by submitting Unicode letters that transform into rejected characters. Attackers can bypass character allowlists and length limits to create reserved-name lookalikes, embed special characters, and exceed the 32-character storage limit."
        }
      ],
      "affected": [
        {
          "vendor": "stoatchat",
          "product": "stoatchat",
          "defaultStatus": "unaffected",
          "versions": [
            {
              "version": "0",
              "status": "affected",
              "versionType": "semver",
              "lessThan": "0.15.5"
            },
            {
              "version": "0.15.5",
              "status": "unaffected",
              "versionType": "semver"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "lang": "en",
              "description": "Incorrect Behavior Order: Validate Before Canonicalize",
              "cweId": "CWE-180",
              "type": "CWE"
            }
          ]
        }
      ],
      "references": [
        {
          "url": "https://github.com/stoatchat/stoatchat/security/advisories/GHSA-qcwh-c934-wrv5",
          "name": "GitHub Security Advisory (GHSA-qcwh-c934-wrv5)",
          "tags": [
            "vendor-advisory"
          ]
        },
        {
          "url": "https://www.vulncheck.com/advisories/stoatchat-before-0.15.5-username-validation-bypass-via-unicode-sanitization",
          "name": "VulnCheck Advisory: stoatchat before 0.15.5 Username Validation Bypass via Unicode Sanitization",
          "tags": [
            "third-party-advisory"
          ]
        }
      ],
      "metrics": [
        {
          "format": "CVSS"
        },
        {
          "format": "CVSS",
          "cvssV3_1": {
            "version": "3.1",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N",
            "attackVector": "NETWORK",
            "attackComplexity": "LOW",
            "privilegesRequired": "LOW",
            "userInteraction": "NONE",
            "scope": "UNCHANGED",
            "confidentialityImpact": "NONE",
            "integrityImpact": "LOW",
            "availabilityImpact": "NONE",
            "baseScore": 4.3,
            "baseSeverity": "MEDIUM"
          }
        }
      ]
    }
  }
}