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MEDIUM severity

FastAPI SSP is vulnerable to Cross-site Request Forgery (CSRF) through improper OAuth parameter validationGHSA-hp6r-r9vc-q8wx

MEDIUMFix: tomasvotava/fastapi-sso@6117d1a

GHSA-hp6r-r9vc-q8wx is a medium-severity (CVSS 6.3) CWE-285 vulnerability in fastapi-sso. A fix is available for fastapi-sso — see the affected versions and patch details below.

Also known asCVE-2025-14546PYSEC-2026-1362
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Nov 4, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

  • CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.

Exploitation and automatability from CISA’s SSVC triage for GHSA-hp6r-r9vc-q8wx.

EPSS Exploitation Probability

via FIRST.org ↗
0.4%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs30th percentile — riskier than 30% of all scored CVEsHighest risk
0.00%0.29%0.57%0.86%0.3%0.4%0.4%0.4%Aug 26Nov 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected
🐍fastapi-sso

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

Versions of the package fastapi-sso before 0.19.0 are vulnerable to Cross-site Request Forgery (CSRF) due to the improper validation of the OAuth state parameter during the authentication callback. While the get_login_url method allows for state generation, it does not persist the state or bind it to the user's session. Consequently, the verify_and_process method accepts the state received in the query parameters without verifying it against a trusted local value. This allows a remote attacker to trick a victim into visiting a malicious callback URL, which can result in the attacker's account being linked to the victim's internal account.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐍PyPIfastapi-ssoall versions0.19.0pip install --upgrade 'fastapi-sso==0.19.0'

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for fastapi-sso, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update fastapi-sso to 0.19.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-hp6r-r9vc-q8wx is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

Versions of the package fastapi-sso before 0.19.0 are vulnerable to Cross-site Request Forgery (CSRF) due to the improper validation of the OAuth state parameter during the authentication callback. While the get_login_url method allows for state generation, it does not persist the state or bind it to the user's session. Consequently, the verify_and_process method accepts the state received in the query parameters without verifying it against a trusted local value. This allows a remote attacker to trick a victim into visiting a malicious callback URL, which can result in the attacker's account
O3 Security · Impact-Aware SCA

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FastAPI SSP is vulnerable to Cross-site Request Forgery…