CVE-2025-47278

Stale session signing via reversed key ordering

Published May 13, 2025 · Updated May 13, 2025

Incorrect key selection in Flask 3.1.0 causes applications using key rotation to sign new sessions with a stale fallback key. SecureCookieSessionInterface.get_signing_serializer places SECRET_KEY before the fallback keys, so itsdangerous selects the final stale key for signing. The condition requires SECRET_KEY_FALLBACKS; signatures remain valid, but applications continue relying on an older key and cannot complete the intended rotation.

CVSS severity1.8
Low
EPSS probability0.18%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incorrect key selection in Flask 3.1.0 causes applications using key rotation to sign new sessions with a stale fallback key. SecureCookieSessionInterface.get_signing_serializer places SECRET_KEY before the fallback keys, so itsdangerous selects the final stale key for signing. The condition requires SECRET_KEY_FALLBACKS; signatures remain valid, but applications continue relying on an older key and cannot complete the intended rotation.

The record

CVE
CVE-2025-47278
Published
May 13, 2025
Updated
May 13, 2025
Vendor
Pallets
Product
Flask
Classifications
CWE-683
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. May 13, 2025CVE publishedPublication date reported by the CVE source.
  2. May 13, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion== 3.1.0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

Pallets · Flaskversion== 3.1.0

Published CVSS scores

1.8GitHubCVSS:4.0/AV:L/AC:L/AT:P/PR:H/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-683Function Call With Incorrect Order of Arguments

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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