CVE-2021-21376
MEDIUMCVE-2021-21376 is a medium-severity (CVSS 6.5) Information Exposure vulnerability in omero-web. O3 Security confirms whether CVE-2021-21376 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
OMERO.web exposes some unnecessary session information in the page
Blast Radius
omero-webReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
OMERO.web is open source Django-based software for managing microscopy imaging. OMERO.web before version 5.9.0 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. This represents an information exposure vulnerability. Some additional information being loaded is not used by the webclient and is being removed in this release. This is fixed in version 5.9.0.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | omero-web | all versions | 5.9.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for omero-web. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update omero-web to 5.9.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-21376 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2021-21376 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2021-21376. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2021-21376 in your dependencies?
O3 detects CVE-2021-21376 across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.