CVE-2021-21377

mediumpriority · track · 22EPSS 0.008 · 57 %ileEUUS
grimoire priorityP3 · Track
Exploitable?
—
no known exploitation
Likely / severe?
0.83% (57th) EPSS
CVSS 4.9 · medium
Is it mine?
3 products
Check your exposure
Who says so?
4 sources
cnnvd · enisa_euvd · osv · nvd

EPSS · scored 2026-10-27

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.

01

cvss

Technical severity, 0–10. One row per scoring source.

5.4
010

base score 0–10 · higher = more severe · hover a vector to decode

v2.04.9mediumAV:N/AC:M/Au:S/C:P/I:P/A:Nprimary · NVD / NIST USexploitability 6.8 · impact 4.9
v3.15.4mediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:Nprimary · NVD / NIST USexploitability 2.3 · impact 2.7
v3.14.8mediumCVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:N/A:Nsecondary · ENISA EU
v3.14.8mediumCVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:N/A:Nsecondary · security-advisories@github.comexploitability 1.2 · impact 3.6
v3.14.8mediumCVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:N/A:Nsecondary · OSV
v3.15mediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N/E:Usecondary · CVSS-BT (t0sche)
02

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-601USCWE-601US
03

affected products (3)

Products and version ranges known to be affected.

04

advisories (2)

Vendor and ecosystem advisories describing this.

  • GHSA-g4rf-pc26-6hmrOMERO webclient does not validate URL redirects on login or switching group.2021-03-23ghsa · osvUS

    ### 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: * Open an issue in [omero-web](https://github.com/ome/omero-web) * Email us at [security](mailto:security@openmicroscopy.org.uk)

  • PYSEC-2021-322021-03-23vendor · osvUS

    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.

05

also known as (6)

Other names and identifiers for this entity.

06

sources

Which sources assert this record, and when.

cnnvdenisa_euvdosvnvdNVDCVE.orgMITRE
published 2021-03-23modified 2026-06-17
07

references (16)

External citations — patches, advisories, analysis.

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