CVE-2025-47278
LOWDescription
Flask is a web server gateway interface (WSGI) web application framework. In Flask 3.1.0, the way fallback key configuration was handled resulted in the last fallback key being used for signing, rather than the current signing key. Signing is provided by the `itsdangerous` library. A list of keys can be passed, and it expects the last (top) key in the list to be the most recent key, and uses that for signing. Flask was incorrectly constructing that list in reverse, passing the signing key first. Sites that have opted-in to use key rotation by setting `SECRET_KEY_FALLBACKS` care likely to unexpectedly be signing their sessions with stale keys, and their transition to fresher keys will be impeded. Sessions are still signed, so this would not cause any sort of data integrity loss. Version 3.1.1 contains a patch for the issue.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v4 Vector
Exploitability
Impact
CVSS:4.0/AV:L/AC:L/AT:P/PR:H/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Exploit Intelligence
Low risk: more likely to be exploited than 8% of all known CVEs.
References
Related Vulnerabilities
Other CWE-683 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2023-32059 | High | 7.5 | 0.7% | - | Fix |
| CVE-2023-5352 | Medium | 4.3 | 0.4% | - | Fix |
| CVE-2026-32269 | Medium | 6.5 | 0.3% | - | Fix |
| CVE-2026-24846 | Medium | 5.5 | 0.2% | - | Fix |
Common questions
How do I fix CVE-2025-47278?
Upgrade flask on debian 13 to 3.1.1-1 or later.
Is CVE-2025-47278 being actively exploited?
Not that we know of. CVE-2025-47278 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.18% is the estimated probability that it will be exploited in the next 30 days. That is higher than 8% of all scored CVEs.
How severe is CVE-2025-47278?
CVE-2025-47278 has a CVSS v4 base score of 1.8, rated low. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2025-47278 affect?
Published advisories record a fix for flask (Debian). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
Embed a live status badge for CVE-2025-47278
Markdown
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-06-17.