# CVE-2021-21377: OMERO webclient does not validate URL redirects on login or switching group.

Source: https://junglewise.ai/threats/cve-2021-21377-omero-webclient-does-not-validate-url-redirects-on-login-or  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2021-03-23  
License: CC BY 4.0 with a link back

CVE-2021-21377 · Severity: low · CVSS 3.1 · Published 2021-03-23

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.

Technologies: [omero-web (PyPI)](https://junglewise.ai/threats/technologies/omero-web). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2021-21377 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2021-21377 being exploited in the wild.

**How severe is CVE-2021-21377?** Low severity, with a CVSS score of 3.1, published 23 March 2021.

**Which products and versions are affected?** omero-web (PyPI) ECOSYSTEM:introduced=0,fixed=5.9.0, GIT:introduced=0,fixed=952f8e5d28532fbb14fb665982211329d137908c|ECOSYSTEM:introduced=0,fixed=5.9.0.

**Is there a fix for CVE-2021-21377?** Yes. omero-web (PyPI): upgrade to 5.9.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected by CVE-2021-21377?** Check whether you run omero-web (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- omero-web (PyPI): upgrade to 5.9.0 or later

  ```sh
  pip install "omero-web>=5.9.0"
  ```


## Affected products

- omero-web (PyPI) ECOSYSTEM:introduced=0,fixed=5.9.0, GIT:introduced=0,fixed=952f8e5d28532fbb14fb665982211329d137908c|ECOSYSTEM:introduced=0,fixed=5.9.0

## Identifiers

- CVE-2021-21377
- GHSA-g4rf-pc26-6hmr
- PYSEC-2021-32

## Related threats

- [PYSEC-2026-1717 - OMERO.web displays unecessary user information when requesting password reset](https://junglewise.ai/threats/cve-2025-54791-omero-web-displays-unecessary-user-information-when-requesting)
- [PYSEC-2026-1718 - OMERO.web must check that the JSONP callback is a valid function](https://junglewise.ai/threats/cve-2024-35180-omero-web-must-check-that-the-jsonp-callback-is-a-valid-function)
- [OMERO.web uses jquery-form library, which may be vulnerable to XSS attack](https://junglewise.ai/threats/omero-web-uses-jquery-form-library-which-may-be-vulnerable-to-xss-1e26aa9c)
- [Inconsistent input sanitisation leads to XSS vectors](https://junglewise.ai/threats/cve-2021-41132-inconsistent-input-sanitisation-leads-to-xss-vectors)
- [OMERO.web exposes some unnecessary session information in the page](https://junglewise.ai/threats/cve-2021-21376-omero-web-exposes-some-unnecessary-session-information-in-the)