CVE-2026-54567
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
- Versión: 3.1
- Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
- Puntuación base: 7.5
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.63%
- Percentil entre todas las CVEs puntuadas: 48
- Fecha de la puntuación: 6/10/2026
EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).
🎯 Técnicas ATT&CK
Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.
- Explotación
T1210Exploitation of Remote Serviceslateral movement75 % - Impacto principal
T1505.003Web Shellpersistence85 % - Impacto secundario
T1059Command and Scripting Interpreterexecution80 % - Impacto secundario
T1565.001Stored Data Manipulationimpact70 %
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
Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.
🛡️ Mitigaciones ATT&CK que cubren estas técnicas
Tecnologías afectadas (2)
⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.
CWE
- CWE-178, CWE-434
Referencias
- https://github.com/jugmac00/flask-reuploaded/commit/5ded76092429c6eb8a4af941b14fbde40a38fff4
- https://github.com/jugmac00/flask-reuploaded/pull/186
- https://github.com/jugmac00/flask-reuploaded/security/advisories/GHSA-937x-gpqr-72gg
- https://github.com/jugmac00/flask-reuploaded/security/advisories/GHSA-937x-gpqr-72gg
JSON original (NVD)
Mostrar
{
"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"
}
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"vulnStatus": "Deferred",
"weaknesses": [
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"source": "security-advisories@github.com",
"description": [
{
"lang": "en",
"value": "CWE-178"
},
{
"lang": "en",
"value": "CWE-434"
}
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}
],
"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"
}