---
id: CVE-2021-21376
aliases:
  - GHSA-gfp2-w5jm-955q
  - PYSEC-2021-31
title: OMERO.web exposes some unnecessary session information in the page
summary: OMERO.web exposes some unnecessary session information in the page
severity: medium
cvss: 6.4
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:N'
vendor: omero-web
product: omero-web
ecosystem: pip
affected:
  - omero-web < 5.9.0
patched:
  - omero-web 5.9.0
published: '2021-03-23'
updated: '2026-09-10'
sourceUpdated: '2026-09-10T03:49:02.354810513Z'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-gfp2-w5jm-955q'
references:
  - url: 'https://github.com/ome/omero-web/security/advisories/GHSA-gfp2-w5jm-955q'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2021-21376'
  - url: >-
      https://github.com/ome/omero-web/commit/952f8e5d28532fbb14fb665982211329d137908c
  - url: 'https://github.com/ome/omero-web'
  - url: 'https://github.com/ome/omero-web/blob/master/CHANGELOG.md#590-march-2021'
  - url: >-
      https://github.com/pypa/advisory-database/tree/main/vulns/omero-web/PYSEC-2021-31.yaml
  - url: 'https://pypi.org/project/omero-web'
  - url: 'https://www.openmicroscopy.org/security/advisories/2021-SV1'
tags:
  - osv
  - pip
epss: 0.01457
epssPercentile: 0.72372
ingestedAt: '2026-09-12T03:13:01.695Z'
---

## Overview

### Background
OMERO.web loads various information about the current user such as their id, name and the groups they are in, and these are available on the main webclient pages. Some additional information being loaded is not used by the webclient and is being removed in this release.

### Impact
OMERO.web before 5.9.0

### Patches
5.9.0

### Workarounds
No workaround

### References

### For more information
If you have any questions or comments about this advisory:
* Open an issue in [omero-web](https://github.com/ome/omero-web)
* Email us at [security](mailto:security@openmicroscopy.org.uk)

## Affected packages

- `omero-web < 5.9.0`

## Remediation

Upgrade to a patched release:

- `omero-web 5.9.0`