Opencast · Opencast · CVE-2021-32623
**Name of the Vulnerable Software and Affected Versions**
Opencast versions prior to 9.6
**Description**
Opencast is vulnerable to the billion laughs attack, which allows an attacker to easily execute a denial of service attack, essentially taking down Opencast using a single HTTP request. To exploit this, users need to have ingest privileges, limiting the group of potential attackers. The attack can be executed by sending a crafted XML file, such as `createMediaPackage.xml`, to an endpoint accepting XML, like `/ingestdownload/ingestdownload`. This causes Opencast to parse the XML and expand the content, consuming a huge amount of memory.
**Recommendations**
To resolve the issue, update to Opencast version 9.6 or later.
As a temporary workaround, consider restricting access to the ingest functionality to minimize the risk of exploitation.
Avoid using endpoints that accept XML, such as `/ingestdownload/ingestdownload`, until the issue is resolved.
There is no known workaround for this issue.