CVE-2021-21376Network attack vector

Authenticated session-data disclosure via serialized eventContext

Published Mar 23, 2021 · Updated Aug 3, 2024

Information exposure in OMERO.web before 5.9.0 allows remote authenticated users to read session details from main webclient pages. The render_response context builder places the complete eventContext into the page, where base_container.html serializes it into WEBCLIENT.eventContext despite the client needing only selected fields. A valid session and access to a main webclient page are required; exposure is limited to the current user's identity, group memberships, and administrative privileges.

CVSS severity6.5
Medium
EPSS probability1.46%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Information exposure in OMERO.web before 5.9.0 allows remote authenticated users to read session details from main webclient pages. The render_response context builder places the complete eventContext into the page, where base_container.html serializes it into WEBCLIENT.eventContext despite the client needing only selected fields. A valid session and access to a main webclient page are required; exposure is limited to the current user's identity, group memberships, and administrative privileges.

The record

CVE
CVE-2021-21376
Published
Mar 23, 2021
Updated
Aug 3, 2024
Vendor
Open Microscopy Environment
Product
OMERO.web
Classifications
CWE-200, T1069, T1087
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 23, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 5.9.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Open Microscopy Environment · OMERO.webversion=< 5.9.0

Published CVSS scores

6.4GitHub Security AdvisoriesCVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:N
5.0NIST NVDAV:N/AC:L/Au:N/C:P/I:N/A:N
6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-200Exposure of Sensitive Information to an Unauthorized Actor
T1069Permission Groups Discovery
T1087Account Discovery

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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