CVE-2021-32623 Opencast vulnerable to billion laughs attack (XML bomb)

What is CVE-2021-32623?

CVE-2021-32623 is a high-severity denial of service vulnerability in opencast, published on 15 Jun 2021. Any signed-in user can exploit it over the network, with no action from the victim.

Official description

Opencast is a free and open source solution for automated video capture and distribution. Versions of Opencast prior to 9.6 are vulnerable to the billion laughs attack, which allows an attacker to easily execute a (seemingly permanent) 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 problem has been fixed in Opencast 9.6. There is no known workaround for this issue.

Weakness: CWE-776

Which versions are affected by CVE-2021-32623?

2 open source packages ship an affected version, including org.opencastproject:opencast-kernel. It affects 1 product.

Products include Apereo Opencast.

How do I fix CVE-2021-32623?

Upgrade org.opencastproject:opencast-kernel to 9.6 or later.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2021-32623 being exploited?

There is no known exploitation of CVE-2021-32623 in the wild and no public exploit code.

Other vulnerabilities in opencast

• CVE-2021-43821 Files Accessible to External Parties in Opencast Critical 9.9
• CVE-2020-5206 Authentication Bypass For Endpoints With Anonymous Access in OpenCast High 8.7
• CVE-2020-5229 Opencast stores passwords using outdated MD5 hash algorithm High 7.7
• CVE-2020-5230 Opencast uses unsafe identifiers High 7.7
• CVE-2020-5228 Opencast allows unauthorized public access via OAI-PMH High 7.6

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-9gwx-9cwp-5c2m.