CVE-2021-43821 Files Accessible to External Parties in Opencast
Attackers with media upload privileges can access local files on the host machine via URL references, potentially exposing sensitive secrets.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2021-43821?
CVE-2021-43821 is a critical path traversal vulnerability in opencast, published on 14 Dec 2021. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
Opencast is an Open Source Lecture Capture & Video Management for Education. Opencast before version 9.10 or 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. Before Opencast 9.10 and 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. An attacker would need to have the privileges required to add new media to exploit this. But these are often widely given. The issue has been fixed in Opencast 10.6 and 11.0. 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.
Weakness: CWE-552
Which versions are affected by CVE-2021-43821?
2 open source packages ship an affected version, including org.opencastproject:opencast-ingest-service-impl. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
org.opencastproject:opencast-ingest-service-impl Maven | All versions | 10.6 |
org.opencastproject:opencast-ingest-service-impl Maven | All versions | 10.6 |
Products include Apereo Opencast.
How do I fix CVE-2021-43821?
Upgrade org.opencastproject:opencast-ingest-service-impl to 10.6 or later.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2021-43821 being exploited?
There is no known exploitation of CVE-2021-43821 in the wild and no public exploit code.
Public exploit code: 1 proofs of concept on GitHub.
Other vulnerabilities in opencast
- CVE-2020-5206 Authentication Bypass For Endpoints With Anonymous Access in OpenCast
- CVE-2021-32623 Opencast vulnerable to billion laughs attack (XML bomb)
- CVE-2020-5229 Opencast stores passwords using outdated MD5 hash algorithm
- CVE-2020-5230 Opencast uses unsafe identifiers
- CVE-2020-5228 Opencast allows unauthorized public access via OAI-PMH
Sources
Also known as GHSA-59g4-hpg3-3gcp.