CVE-2026-40035

What it is

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.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of data exposure, data tampering.

Exploit odds

0.6% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-04-08 22:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-10-08 16:17 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.6% in the next 30 days (EPSS).
• Severity: 9.3 CRITICAL (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2026-04-08 22:16 UTC

Last modified

2026-10-08 16:17 UTC

Exploit probability

0.6% · EPSS, next 30 days

Weakness

CWE-489

Record status

Analyzed

Affected

• Ryandfir Unfurl ≤ 2025.08

Attack profile CVSS 4.0 · 9.3

Attack vector

Network

Complexity

Low

Attack requirements

None

Privileges needed

None

User interaction

None

Confidentiality

High

Integrity

High

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-40035.md and follow it. Check whether this project is affected by CVE-2026-40035. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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