How severe is CVE-2021-21377?

CVE-2021-21377 has a CVSS 3.x base score of 4.8, rated medium severity. It is exploitable over network with high attack complexity, requires low privileges and user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2021-21377 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (53rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-21377?

CVE-2021-21377 affects Openmicroscopy Omero.web. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-21377?

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

When was CVE-2021-21377 published?

CVE-2021-21377 was published on 2021-03-23 and last updated on 2026-06-17.

CVE-2021-21377

CVE-2021-21377 is a medium-severity vulnerability in Openmicroscopy Omero.web with a CVSS 3.x base score of 4.8. 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 4.8)
CVSS v2: 4.9
EPSS exploit prediction: 1% (53rd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-601
Affected product: Openmicroscopy Omero.web
Published: 2021-03-23
Last modified: 2026-06-17

Description

OMERO.web is open source Django-based software for managing microscopy imaging. OMERO.web before version 5.9.0 supports redirection to a given URL after performing login or switching the group context. These URLs are not validated, allowing redirection to untrusted sites. OMERO.web 5.9.0 adds URL validation before redirecting. External URLs are not considered valid, unless specified in the omero.web.redirect_allowed_hosts setting.

Frequently asked questions

What is CVE-2021-21377?: OMERO.web is open source Django-based software for managing microscopy imaging. OMERO.web before version 5.9.0 supports redirection to a given URL after performing login or switching the group context. These URLs are not validated, allowing redirection to untrusted sites. OMERO.web 5.9.0 adds URL validation before redirecting. External URLs are not considered valid, unless specified in the omero.web.redirect_allowed_hosts setting.
How severe is CVE-2021-21377?: CVE-2021-21377 has a CVSS 3.x base score of 4.8, rated medium severity. It is exploitable over network with high attack complexity, requires low privileges and user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2021-21377 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (53rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-21377?: CVE-2021-21377 affects Openmicroscopy Omero.web. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-21377?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-21377 published?: CVE-2021-21377 was published on 2021-03-23 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:openmicroscopy:omero.web:*:*:*:*:*:*:*:*

More vulnerabilities in Openmicroscopy Omero.web

CVE-2021-21376 — Medium (CVSS 6.4): OMERO.web is open source Django-based software for managing microscopy imaging. OMERO.web before version 5.9.0 loads…
CVE-2020-7932 — Medium (CVSS 5.7): OMERO.web before 5.6.3 optionally allows sensitive data elements (e.g., a session key) to be passed as URL query…

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