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CVE-2026-54567 (GCVE-0-2026-54567)

Vulnerability from cvelistv5 – Published: 2026-09-14 17:15 – Updated: 2026-09-14 17:16
VLAI
Title
Flask-Reuploaded: Extension-denylist bypass via case-folding asymmetry in name-override path (incomplete-fix variant of CVE-2026-27641)
Summary
Flask-Reuploaded provides file uploads for Flask. From 1.5.0 until 1.6.0, UploadSet.save(storage, name=...) in src/flask_uploads/flask_uploads.py applies lowercase_ext to the default upload path but uses the case-preserving extension helper for a caller-supplied name before extension_allowed evaluates an AllExcept denylist. An attacker who controls the name override can use a mixed-case dangerous extension to bypass a lowercase denylist and store the file in the served upload directory. Exploitation requires a denylist configuration, a user-influenced name override, and a deployment that resolves or executes extensions case-insensitively; pure allowlists remain protected and path containment is not bypassed. On an execution-capable upload directory, the stored file can execute with the web server's privileges and affect confidentiality, integrity, and availability. This issue is fixed in version 1.6.0.
Severity
7.5 (High)
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
CWE
  • CWE-178 - Improper Handling of Case Sensitivity
  • CWE-434 - Unrestricted Upload of File with Dangerous Type
Assigner
References
Impacted products
Vendor Product Version CPE status
jugmac00 flask-reuploaded Affected: < 1.6.0
guessed Create a notification for this product.
Show details on NVD website
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "product": "flask-reuploaded",
          "vendor": "jugmac00",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 1.6.0"
            }
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          "value": "Flask-Reuploaded provides file uploads for Flask. From 1.5.0 until 1.6.0, UploadSet.save(storage, name=...) in src/flask_uploads/flask_uploads.py applies lowercase_ext to the default upload path but uses the case-preserving extension helper for a caller-supplied name before extension_allowed evaluates an AllExcept denylist. An attacker who controls the name override can use a mixed-case dangerous extension to bypass a lowercase denylist and store the file in the served upload directory. Exploitation requires a denylist configuration, a user-influenced name override, and a deployment that resolves or executes extensions case-insensitively; pure allowlists remain protected and path containment is not bypassed. On an execution-capable upload directory, the stored file can execute with the web server\u0027s privileges and affect confidentiality, integrity, and availability. This issue is fixed in version 1.6.0."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "HIGH",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "HIGH",
            "integrityImpact": "HIGH",
            "privilegesRequired": "LOW",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-178",
              "description": "CWE-178: Improper Handling of Case Sensitivity",
              "lang": "en",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-434",
              "description": "CWE-434: Unrestricted Upload of File with Dangerous Type",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-14T17:16:08.820Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/jugmac00/flask-reuploaded/security/advisories/GHSA-937x-gpqr-72gg",
          "tags": [
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          ],
          "url": "https://github.com/jugmac00/flask-reuploaded/security/advisories/GHSA-937x-gpqr-72gg"
        },
        {
          "name": "https://github.com/jugmac00/flask-reuploaded/pull/186",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/jugmac00/flask-reuploaded/pull/186"
        },
        {
          "name": "https://github.com/jugmac00/flask-reuploaded/commit/5ded76092429c6eb8a4af941b14fbde40a38fff4",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/jugmac00/flask-reuploaded/commit/5ded76092429c6eb8a4af941b14fbde40a38fff4"
        }
      ],
      "source": {
        "advisory": "GHSA-937x-gpqr-72gg",
        "discovery": "UNKNOWN"
      },
      "title": "Flask-Reuploaded: Extension-denylist bypass via case-folding asymmetry in name-override path (incomplete-fix variant of CVE-2026-27641)"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-54567",
    "datePublished": "2026-09-14T17:15:49.272Z",
    "dateReserved": "2026-06-15T19:15:27.343Z",
    "dateUpdated": "2026-09-14T17:16:08.820Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-54567\",\"sourceIdentifier\":\"security-advisories@github.com\",\"published\":\"2026-09-14T18:17:53.547\",\"lastModified\":\"2026-09-14T18:17:53.547\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"Flask-Reuploaded provides file uploads for Flask. From 1.5.0 until 1.6.0, UploadSet.save(storage, name=...) in src/flask_uploads/flask_uploads.py applies lowercase_ext to the default upload path but uses the case-preserving extension helper for a caller-supplied name before extension_allowed evaluates an AllExcept denylist. An attacker who controls the name override can use a mixed-case dangerous extension to bypass a lowercase denylist and store the file in the served upload directory. Exploitation requires a denylist configuration, a user-influenced name override, and a deployment that resolves or executes extensions case-insensitively; pure allowlists remain protected and path containment is not bypassed. On an execution-capable upload directory, the stored file can execute with the web server\u0027s privileges and affect confidentiality, integrity, and availability. This issue is fixed in version 1.6.0.\"}],\"affected\":[{\"source\":\"security-advisories@github.com\",\"affectedData\":[{\"vendor\":\"jugmac00\",\"product\":\"flask-reuploaded\",\"versions\":[{\"version\":\"\u003c 1.6.0\",\"status\":\"affected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H\",\"baseScore\":7.5,\"baseSeverity\":\"HIGH\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"HIGH\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.6,\"impactScore\":5.9}]},\"weaknesses\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Primary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-178\"},{\"lang\":\"en\",\"value\":\"CWE-434\"}]}],\"references\":[{\"url\":\"https://github.com/jugmac00/flask-reuploaded/commit/5ded76092429c6eb8a4af941b14fbde40a38fff4\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/jugmac00/flask-reuploaded/pull/186\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/jugmac00/flask-reuploaded/security/advisories/GHSA-937x-gpqr-72gg\",\"source\":\"security-advisories@github.com\"}]}}"
  }
}



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