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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.

PUBLISHED Reserved 2026-04-08 | Published 2026-04-08 | Updated 2026-04-09 | Assigner VulnCheck




CRITICAL: 9.3CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

CRITICAL: 9.1CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Problem types

CWE-489 Active Debug Code

Product status

Default status
unaffected

Any version
affected

Credits

Mobasi Security Team reporter

References

github.com/...unfurl/security/advisories/GHSA-vg9h-jx4v-cwx2 exploit

github.com/...unfurl/security/advisories/GHSA-vg9h-jx4v-cwx2 (GHSA Advisory GHSA-vg9h-jx4v-cwx2) vendor-advisory

www.vulncheck.com/...gger-exposure-via-string-config-parsing (VulnCheck Advisory: dfir-unfurl - Werkzeug Debugger Exposure via String Config Parsing) third-party-advisory

cve.org (CVE-2026-40035)

nvd.nist.gov (CVE-2026-40035)

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