Summary
Files Accessible to External Parties in Opencast
Opencast before version 10.6 allows references to local file URLs in ingested media packages, allowing attackers to include local files from Opencast's host machines and making them available via the web interface.
Workarounds
You can mitigate this issue by narrowing down the read access Opencast has to files on the file system using UNIX permissions or mandatory access control systems like SELinux. This cannot prevent access to files Opencast needs to read though and we highly recommend updating.
References
For more information
If you have any questions or comments about this advisory:
- Open an issue in our issue tracker
- Email us at [email protected]
Impact
Before Opencast 10.6, Opencast would open and include local files during ingests. Attackers could exploit this to include most local files the process has read access to, extracting secrets from the host machine.
For example, to expose the custom.properties of develop.opencast.org via the asset manager, an attacker could have run:
curl -f -i -u admin:opencast \
https://develop.opencast.org/ingest/addMediaPackage/fast \
-F 'flavor=presenter/source'\
-F mediaUri=file:///srv/opencast/opencast-dist-allinone/etc/custom.properties\
-F title="custom.properties"
An attacker would need to have the privileges required to add new media to exploit this. But these are often widely given.
CVE-2021-43821 has a CVSS score of 9.9 (Critical). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (10.6); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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The issue has been fixed in Opencast 10.6 and 11.0.
Frequently Asked Questions
- What is CVE-2021-43821? CVE-2021-43821 is a critical-severity security vulnerability in org.opencastproject:opencast-ingest-service-impl (maven), affecting versions < 10.6. It is fixed in 10.6.
- How severe is CVE-2021-43821? CVE-2021-43821 has a CVSS score of 9.9 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of org.opencastproject:opencast-ingest-service-impl are affected by CVE-2021-43821? org.opencastproject:opencast-ingest-service-impl (maven) versions < 10.6 is affected.
- Is there a fix for CVE-2021-43821? Yes. CVE-2021-43821 is fixed in 10.6. Upgrade to this version or later.
- Is CVE-2021-43821 exploitable, and should I be worried? Whether CVE-2021-43821 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2021-43821 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2021-43821? Upgrade
org.opencastproject:opencast-ingest-service-implto 10.6 or later.