CVE Vulnerabilities

CVE-2021-32623

Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion')

Published: Jun 16, 2021 | Modified: Jun 23, 2021
CVSS 3.x
6.5
MEDIUM
Source:
NVD
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
CVSS 2.x
4 MEDIUM
AV:N/AC:L/Au:S/C:N/I:N/A:P
RedHat/V2
RedHat/V3
Ubuntu

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

The product uses XML documents and allows their structure to be defined with a Document Type Definition (DTD), but it does not properly control the number of recursive definitions of entities.

Affected Software

Name Vendor Start Version End Version
Opencast Apereo * 9.6 (excluding)

Potential Mitigations

References