# CVE-2025-47278: python3-flask: Flask is a web server gateway interface (WSGI) web application framework.In Flask 3.1.0, the way fallback key configu...

CVE-2025-47278 is fixed in 2 products on 1 platform, first by DEBIAN-CVE-2025-47278, released May 13, 2025. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2025-47278
- Priority: Routine
- CVSS: n/a (Medium)
- EPSS: 0.0019
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: May 13, 2025

## Description

Flask is a web server gateway interface (WSGI) web application framework.In Flask 3.1.0, the way fallback key configuration was handled resulted inthe last fallback key being used for signing, rather than the currentsigning key. Signing is provided by the `itsdangerous` library. A list ofkeys can be passed, and it expects the last (top) key in the list to be themost recent key, and uses that for signing. Flask was incorrectlyconstructing that list in reverse, passing the signing key first. Sitesthat have opted-in to use key rotation by setting `SECRET_KEY_FALLBACKS`care likely to unexpectedly be signing their sessions with stale keys, andtheir transition to fresher keys will be impeded. Sessions are stillsigned, so this would not cause any sort of data integrity loss. Version3.1.1 contains a patch for the issue.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | flask Debian 13.5 (trixie) | 3.1.1-1 | [DEBIAN-CVE-2025-47278](https://patchblox.com/security/data/fix/linux/debian-cve-2025-47278.md) | May 13, 2025 |
| Linux | flask Debian 14 | 3.1.1-1 | [DEBIAN-CVE-2025-47278](https://patchblox.com/security/data/fix/linux/debian-cve-2025-47278.md) | May 13, 2025 |
| Linux | python3-flask Ubuntu 25.04 (plucky) | 3.1.0-2ubuntu1.1 | [python3-flask 3.1.0-2ubuntu1.1](https://patchblox.com/security/data/fix/linux/ubuntu-plucky-python3-flask-3.1.0-2ubuntu1.1.md) | Jan 16, 2026 |

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Data as of 2026-11-09T01:18:40Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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