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CVE-2025-47278— Flask uses fallback key instead of current signing key

Quick assessment

Affected
pallets flask
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Flask是Pallets开源的一个用于构建web应用程序的Python微框架。 Flask 3.1.0版本存在安全漏洞，该漏洞源于密钥回退配置处理不当，可能导致使用过期的密钥进行会话签名。

AI Predicted 5.3 Difficulty: Theoretical EPSS 0.18% · P7

Possible ATT&CK Techniques 1 AI

T1556 · Modify Authentication Process
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I. Basic Information for CVE-2025-47278

Vulnerability Information
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Vulnerability Title
Flask uses fallback key instead of current signing key
Source: CVE Program / CVE List V5
Vulnerability 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 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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
使用不正确参数次序的函数调用
Source: CVE Program / CVE List V5
Vulnerability Title
Flask 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Flask是Pallets开源的一个用于构建web应用程序的Python微框架。 Flask 3.1.0版本存在安全漏洞，该漏洞源于密钥回退配置处理不当，可能导致使用过期的密钥进行会话签名。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
pallets flask = 3.1.0 -

II. Public POCs for CVE-2025-47278

# POC Description Source Link Shenlong Link
AI-Generated POC Verified env Premium
Reproduced successfully in a real sandbox · Below is the actual recording of building the environment and exploiting the vulnerability.
Success marker: VULNERABLE: Flask 3.1.0 is signing sessions with fallback/stale key "oldest_key_123" instead of current key "current_key_ABC" (CVE-2025-47278 key-ordering bug)
Reproduction recording is a Pro+ exclusive
Watch the full sandbox build + live exploit recording for this CVE. Limited-time ¥499/mo.
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claude_code · 5113 chars
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III. Intelligence Information for CVE-2025-47278

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IV. Related Vulnerabilities

Same product: flask
Same vendor: pallets
Same weakness: CWE-683

V. Comments for CVE-2025-47278

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