How severe is CVE-2026-40035?

CVE-2026-40035 has a CVSS 3.x base score of 9.1, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.

Is CVE-2026-40035 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (42nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-40035?

CVE-2026-40035 affects Ryandfir Unfurl. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-40035?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

Does CVE-2026-40035 have an EU (EUVD) identifier?

Yes. CVE-2026-40035 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-20777.

When was CVE-2026-40035 published?

CVE-2026-40035 was published on 2026-04-08 and last updated on 2026-06-17.

CVE-2026-40035

CVE-2026-40035 is a critical-severity vulnerability in Ryandfir Unfurl with a CVSS 3.x base score of 9.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-489.

Key facts

Severity: Critical (CVSS 3.x base score 9.1)
CVSS v4: 9.3
EPSS exploit prediction: 1% (42nd percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-20777
Weakness: CWE-489
Affected product: Ryandfir Unfurl
Published: 2026-04-08
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2026-40035?: 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.
How severe is CVE-2026-40035?: CVE-2026-40035 has a CVSS 3.x base score of 9.1, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2026-40035 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (42nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-40035?: CVE-2026-40035 affects Ryandfir Unfurl. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-40035?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
Does CVE-2026-40035 have an EU (EUVD) identifier?: Yes. CVE-2026-40035 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-20777.
When was CVE-2026-40035 published?: CVE-2026-40035 was published on 2026-04-08 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:ryandfir:unfurl:*:*:*:*:*:*:*:*

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