CVE-2021-21377
Open Redirect in OMERO.web
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- High
- Privileges needed
- Low
- User interaction
- Required
What an attacker can affect
- Confidentiality
- High
- Integrity
- None
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
Open Redirect in OMERO.web
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.
- Record
CVE-2021-21377- CVSS 3.1
- 4.8 Medium
CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:N/A:N - Weakness
- CWE-601
- Updated
- 2026-11-02
EUVDEUVD-2021-0158
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.
- Record
EUVD-2021-0158- CVSS 3.1
- 4.8 Medium
CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:N/A:N - Updated
- 2026-11-03
GitHub AdvisoriesGHSA-g4rf-pc26-6hmr
OMERO webclient does not validate URL redirects on login or switching group.
Background
OMERO.web 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.
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:
- Record
GHSA-g4rf-pc26-6hmr- CVSS 4.0
- 5.9 Medium
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N - CVSS 3.1
- 4.8 Medium
CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:N/A:N - Weakness
- CWE-601
- Updated
- 2026-11-02
NVD
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.
- Record
CVE-2021-21377- CVSS 3.1
- 4.8 Medium
CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:N/A:N - CVSS 3.1
- 5.4 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N - CVSS 2.0
- 4.9 Medium
AV:N/AC:M/Au:S/C:P/I:P/A:N - Weakness
- CWE-601
- Updated
- 2026-11-02
OSV
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.
- Record
CVE-2021-21377- CVSS 3.1
- 5.4 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N - Updated
- 2026-11-02
OSVGHSA-g4rf-pc26-6hmr
OMERO webclient does not validate URL redirects on login or switching group.
Background
OMERO.web 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.
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:
- Record
GHSA-g4rf-pc26-6hmr- CVSS 4.0
- 5.9 Medium
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N - CVSS 3.1
- 4.8 Medium
CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:N/A:N - Weakness
- CWE-601
- Updated
- 2026-11-02
OSVPYSEC-2021-32 No score
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.
- Record
PYSEC-2021-32- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
omero-webPyPI |
before 5.9.0 | 5.9.0 |
omero-webPyPI |
before 5.9.0, plus listed versions 5.5.dev15.5.dev25.6.05.6.15.6.2 Show 12 moreShow less5.6.35.6.dev15.6.dev25.6.dev35.6.dev45.6.dev55.6.dev65.6.dev75.7.05.7.15.8.05.8.1 |
5.9.0 |
omero-webPyPI |
before 5.9.0, plus listed versions 5.5.dev15.5.dev25.6.dev15.6.dev25.6.dev3 Show 12 moreShow less5.6.dev45.6.dev55.6.dev65.6.dev75.6.05.6.15.6.25.6.35.7.05.7.15.8.05.8.1 |
5.9.0 |
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-21377 is a medium vulnerability (CVSS 4.8) in Openmicroscopy Omero.web, published March 23, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.83%, the 57th percentile. Fixed in omero-web 5.9.0.
References
pypi.org/project/omero-web
github.com/ome/omero-web/blob/master/CHANGELOG.md
openmicroscopy.org/security/advisories/2021-SV2
nvd.nist.gov/vuln/detail/CVE-2021-21377