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CVE-2026-40035

9.1 · CRITICAL

Unfurl through 2025.08 contains an improper input validation vulnerability in config parsing that enables Flask debug mode by default.

Published Apr 8, 2026CWE-489EPSS 0.72%

Overview

CVE-2026-40035 is a critical-severity vulnerability. It was published on April 8, 2026 and has a CVSS 3.1 base score of 9.1 (CRITICAL).

This vulnerability has a CVSS 3.1 base score of 9.1, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical description

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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/obsidianforensics/unfurl/security/advisories/GHSA-vg9h-jx4v-cwx2Refwww.vulncheck.com/advisories/dfir-unfurl-werkzeug-debugger-exposure-via-string-config-parsingGitHubgithub.com/obsidianforensics/unfurl/security/advisories/GHSA-vg9h-jx4v-cwx2

How CyberStrike helps

Frequently asked questions

What is CVE-2026-40035?

CVE-2026-40035 is a critical-severity vulnerability. It was published on April 8, 2026 and has a CVSS 3.1 base score of 9.1 (CRITICAL).

How severe is CVE-2026-40035?

This vulnerability has a CVSS 3.1 base score of 9.1, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-40035?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-40035?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-40035 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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