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CVE-2026-54567

Status: DeferredHigh (7.5)—

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.

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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.

CVSS

Exploitation probability (EPSS)

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

🎯 ATT&CK techniques

How this vulnerability is exploited and what the attacker gains, in MITRE ATT&CK terms.

Vulnerabilidad de bypass de denylist en Flask-Reuploaded que permite a un atacante autenticado (PR:L) subir una web shell cambiando la extensión a mayúsculas para evadir validaciones. Requiere acceso autenticado a la red y explotación de servicio remoto (T1210). El impacto principal es la creación d

Inferred by our analysis agent from the official description, CVSS vector and CWE, and checked by a supervisor. May contain errors.

🛡️ ATT&CK mitigations that cover these techniques

Disable or Remove Feature or ProgramPrivileged Account ManagementVulnerability ScanningUser Account ManagementThreat Intelligence ProgramRestrict Web-Based Content

Affected technologies (2)

⚠ AI-inferred from the description — NVD hasn't analyzed this CVE yet, these aren't verified CPEs.

Jugmac00 — Flask-reuploadedAIPalletsprojects — FlaskAI

CWEs

References

Raw JSON (NVD)

Show
{
  "id": "CVE-2026-54567",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-54567",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-09-16T15:22:17.514494Z"
        }
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "security-advisories@github.com",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 7.5,
          "attackVector": "NETWORK",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "HIGH",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 5.9,
        "exploitabilityScore": 1.6
      }
    ]
  },
  "affected": [
    {
      "source": "security-advisories@github.com",
      "affectedData": [
        {
          "vendor": "jugmac00",
          "product": "flask-reuploaded",
          "versions": [
            {
              "status": "affected",
              "version": "< 1.6.0"
            }
          ]
        }
      ]
    }
  ],
  "published": "2026-09-14T18:17:53.547",
  "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"
    },
    {
      "url": "https://github.com/jugmac00/flask-reuploaded/security/advisories/GHSA-937x-gpqr-72gg",
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0"
    }
  ],
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "security-advisories@github.com",
      "description": [
        {
          "lang": "en",
          "value": "CWE-178"
        },
        {
          "lang": "en",
          "value": "CWE-434"
        }
      ]
    }
  ],
  "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's privileges and affect confidentiality, integrity, and availability. This issue is fixed in version 1.6.0."
    }
  ],
  "lastModified": "2026-09-30T17:51:56.193",
  "sourceIdentifier": "security-advisories@github.com"
}