How severe is CVE-2020-4037?

CVE-2020-4037 has a CVSS 3.x base score of 4.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity none, and availability none.

Is CVE-2020-4037 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (55th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-4037?

CVE-2020-4037 affects Oauth2 Proxy Project Oauth2 Proxy. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2020-4037?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2020-4037 published?

CVE-2020-4037 was published on 2020-06-29 and last updated on 2026-06-17.

CVE-2020-4037

CVE-2020-4037 is a medium-severity vulnerability in Oauth2 Proxy Project Oauth2 Proxy with a CVSS 3.x base score of 4.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-601.

Key facts

Severity: Medium (CVSS 3.x base score 4.3)
CVSS v2: 5.8
EPSS exploit prediction: 1% (55th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-601
Affected product: Oauth2 Proxy Project Oauth2 Proxy
Published: 2020-06-29
Last modified: 2026-06-17

Description

In OAuth2 Proxy from version 5.1.1 and less than version 6.0.0, users can provide a redirect address for the proxy to send the authenticated user to at the end of the authentication flow. This is expected to be the original URL that the user was trying to access. This redirect URL is checked within the proxy and validated before redirecting the user to prevent malicious actors providing redirects to potentially harmful sites. This has been fixed in version 6.0.0.

Frequently asked questions

What is CVE-2020-4037?: In OAuth2 Proxy from version 5.1.1 and less than version 6.0.0, users can provide a redirect address for the proxy to send the authenticated user to at the end of the authentication flow. This is expected to be the original URL that the user was trying to access. This redirect URL is checked within the proxy and validated before redirecting the user to prevent malicious actors providing redirects to potentially harmful sites. This has been fixed in version 6.0.0.
How severe is CVE-2020-4037?: CVE-2020-4037 has a CVSS 3.x base score of 4.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity none, and availability none.
Is CVE-2020-4037 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (55th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-4037?: CVE-2020-4037 affects Oauth2 Proxy Project Oauth2 Proxy. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2020-4037?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2020-4037 published?: CVE-2020-4037 was published on 2020-06-29 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:oauth2_proxy_project:oauth2_proxy:*:*:*:*:*:*:*:*

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