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CVE-2026-40035

CRITICAL CVSS 4.0: 9.3 EPSS 0.12%
Updated Apr 17, 2026
Flask
Parameter Value
CVSS 9.3 (CRITICAL)
Affected Versions before 2025.08
Type CWE-489
Vendor Flask
Public PoC No

Unfurl through 2025.08 contains an improper input validation vulnerability in config parsing that enables Flask debug mode by default. The debug configuration value is read as a string and passed directly to app.run(), causing any non-empty string to evaluate truthy, allowing attackers to access the Werkzeug debugger and disclose sensitive information or achieve remote code execution.

Attack Parameters

Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Attack Requirements
None
No additional conditions
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed

Impact Assessment

Confidentiality
High
Complete data leak
Integrity
High
Complete data modification
Availability
None
No disruption

CVSS Vector v4.0

Weakness Type (CWE)

Vulnerable Products 1

Configuration From (including) Up to (excluding)
Ryandfir Unfurl
cpe:2.3:a:ryandfir:unfurl:*:*:*:*:*:*:*:*
<= 2025.08