How severe is CVE-2021-21337?

CVE-2021-21337 has a CVSS 3.x base score of 5.7, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2021-21337 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 8% (94th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-21337?

CVE-2021-21337 affects Zope Products.pluggableauthservice. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-21337?

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

When was CVE-2021-21337 published?

CVE-2021-21337 was published on 2021-03-08 and last updated on 2026-06-17.

CVE-2021-21337

CVE-2021-21337 is a medium-severity vulnerability in Zope Products.pluggableauthservice with a CVSS 3.x base score of 5.7. 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 5.7)
CVSS v2: 5.8
EPSS exploit prediction: 8% (94th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-601
Affected product: Zope Products.pluggableauthservice
Published: 2021-03-08
Last modified: 2026-06-17

Description

Products.PluggableAuthService is a pluggable Zope authentication and authorization framework. In Products.PluggableAuthService before version 2.6.0 there is an open redirect vulnerability. A maliciously crafted link to the login form and login functionality could redirect the browser to a different website. The problem has been fixed in version 2.6.1. Depending on how you have installed Products.PluggableAuthService, you should change the buildout version pin to `2.6.1` and re-run the buildout, or if you used `pip` simply do `pip install "Products.PluggableAuthService>=2.6.1".

Frequently asked questions

What is CVE-2021-21337?: Products.PluggableAuthService is a pluggable Zope authentication and authorization framework. In Products.PluggableAuthService before version 2.6.0 there is an open redirect vulnerability. A maliciously crafted link to the login form and login functionality could redirect the browser to a different website. The problem has been fixed in version 2.6.1. Depending on how you have installed Products.PluggableAuthService, you should change the buildout version pin to `2.6.1` and re-run the buildout, or if you used `pip` simply do `pip install "Products.PluggableAuthService>=2.6.1".
How severe is CVE-2021-21337?: CVE-2021-21337 has a CVSS 3.x base score of 5.7, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2021-21337 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 8% (94th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-21337?: CVE-2021-21337 affects Zope Products.pluggableauthservice. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-21337?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-21337 published?: CVE-2021-21337 was published on 2021-03-08 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:zope:products.pluggableauthservice:*:*:*:*:*:*:*:*

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