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Medium, CVSS 5.3amended

Flask-Security-Too: WebAuthn reauthentication freshness bypass via cross-user assertion

GHSA-f66q-9rf6-8795

What to do

Vendor response not established. Follow the primary source's mitigation guidance and check back for a fix.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • PyPI flask-security-too

    Affected
    >= 5.8.0, <= 5.8.1
    Fixed in
    no fixed version recorded

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS 4.0
5.3 · CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N · score source
EPSS
No dated EPSS signal available.
Source description

As published by the source; long descriptions are shortened.

Summary Flask-Security-Too 5.8.0 and 5.8.1 mark a session as reauthentication-fresh after processing a WebAuthn assertion whose proven credential belongs to a different user than the currently authenticated session user. The check that GHSA-97r5-pg8x-p63p added on the OAuth reauthentication path (user.email == currentuser.email) is missing on the WebAuthn reauthentication path. An attacker who owns any WebAuthn credential registered to any account on the deployment can satisfy a victim session's freshness gate by submitting their own WebAuthn proof into the victim session. Affected versions Flask-Security-Too = 5.8.0, <= 5.8.1 (current main commit 5c44c76e33a20b67d02115e26d2da4bab18c094e). GHSA-97r5-pg8x-p63p (published 2026-05-22) shipped its fix in 5.8.1 only on oauthglue.py; webauthn.py was not touched and remains exploitable in 5.8.1. Privilege required Authenticated attacker on the same Flask-Security deployment, owning at least one WebAuthn credential of any usage (first /…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 3 · amended ·

    Amended from ghsa record GHSA-f66q-9rf6-8795

  2. Revision 2 · amended ·

    Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

  3. Revision 1 · created ·

    Published from osv record GHSA-f66q-9rf6-8795

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: GHSA-f66q-9rf6-8795

Advisory: Flask-Security-Too: WebAuthn reauthentication freshness bypass via cross-user assertion
IDs: GHSA-f66q-9rf6-8795
Record: https://patchnext.com/advisories/ghsa-f66q-9rf6-8795 (revision 3, source checked 26 Oct 2026, 13:46 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor response not established. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI flask-security-too: affected >= 5.8.0, <= 5.8.1

## Suggested inspection (read-only)
- `python -m pip show flask-security-too`: prints the installed version. Run with the environment that serves production active.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on flask-security-too.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-f66q-9rf6-8795 (OSV record GHSA-f66q-9rf6-8795 lists affected ranges: PyPI flask-security-too >=5.8.0 <=5.8.1)
- Verified: https://github.com/advisories/GHSA-f66q-9rf6-8795 (GitHub-reviewed advisory GHSA-f66q-9rf6-8795 lists affected ranges: PyPI flask-security-too >=5.8.0 <=5.8.1)

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