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CVE-2025-14546

FastAPI SSP is vulnerable to Cross-site Request Forgery (CSRF) through improper OAuth parameter validation

6.9 MediumFix available

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.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
Low
User interaction
Active

What an attacker can affect

Confidentiality
High
Integrity
Low
Availability
None

Exploit likelihood

0.36%Up 0.3 points since Dec 19, 2025
90%50%10%1%

What each source reports

CVE List Score used 6.9

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.

Record
CVE-2025-14546
CVSS 4.0
6.9 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N/E:P
CVSS 3.1
6.3 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:L/A:N/E:P
Weakness
CWE-285
Updated
2026-11-02
EUVDEUVD-2025-204438 6.9

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.

Record
EUVD-2025-204438
CVSS 4.0
6.9 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N/E:P
Updated
2026-11-02
GitHub AdvisoriesGHSA-hp6r-r9vc-q8wx 5.4

FastAPI SSP is vulnerable to Cross-site Request Forgery (CSRF) through improper OAuth parameter validation

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.

Record
GHSA-hp6r-r9vc-q8wx
CVSS 4.0
5.4 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N/E:P
CVSS 3.1
6.3 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:L/A:N
Weakness
CWE-285
Updated
2026-11-02
NVD 5.4

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.

Record
CVE-2025-14546
CVSS 4.0
5.4 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1
6.3 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:L/A:N
Weakness
CWE-285
Updated
2026-11-02
OSV 5.4

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.

Record
CVE-2025-14546
CVSS 4.0
5.4 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N/E:P
Weakness
CWE-285
Updated
2026-11-02
OSVGHSA-hp6r-r9vc-q8wx 5.4

FastAPI SSP is vulnerable to Cross-site Request Forgery (CSRF) through improper OAuth parameter validation

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.

Record
GHSA-hp6r-r9vc-q8wx
CVSS 4.0
5.4 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N/E:P
CVSS 3.1
6.3 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:L/A:N
Weakness
CWE-285
Updated
2026-11-02
OSVPYSEC-2026-1362 5.4

FastAPI SSP is vulnerable to Cross-site Request Forgery (CSRF) through improper OAuth parameter validation

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.

Record
PYSEC-2026-1362
CVSS 4.0
5.4 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N/E:P
CVSS 3.1
6.3 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:L/A:N
Updated
2026-11-02

Affected packages

Affected packages
PackageAffectedFixed
fastapi-sso
PyPI
before 0.19.0
0.19.0
fastapi-sso
PyPI
before 0.19.0, plus listed versions
0.10.00.11.00.12.00.12.10.12.2
Show 38 moreShow less
0.13.00.13.10.14.00.14.10.14.20.15.00.16.00.17.00.18.00.2.10.2.100.2.110.2.120.2.130.2.20.2.30.2.40.2.50.2.60.2.70.2.80.2.90.3.00.4.00.5.00.5.10.6.10.6.20.6.30.6.40.7.00.7.10.7.20.7.30.7.40.8.00.9.00.9.1
0.19.0

History

History
RecordedChangedSources
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2025-14546 is a medium vulnerability (CVSS 6.9) in fastapi-sso, published December 19, 2025. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.36%, the 29th percentile. Fixed in fastapi-sso 0.19.0.

References

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