PT-2021-19815 · Opencast · Opencast

Lkiesow · Published 2021-06-15 · Updated 2021-06-23 · CVE-2021-32623

Positive Technologies (AI Summary)

CVSS v3.1

8.1

High

Base vector

AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H

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.

Exploit

Fix

XML Entity Expansion

Weakness Enumeration

CWE-776

Related Identifiers

CVE-2021-32623

GHSA-9GWX-9CWP-5C2M

Affected Products

Opencast

References · 9

• 🔥 https://github.com/opencast/opencast/security/advisories/GHSA-9gwx-9cwp-5c2m · Exploit
• https://github.com/opencast/opencast/commit/8ae27da5a6f658011a5741b3210e715b0dc6213e · Patch
• https://nvd.nist.gov/vuln/detail/CVE-2021-32623 · Security Note
• https://osv.dev/vulnerability/CVE-2021-32623 · Vendor Advisory
• https://osv.dev/vulnerability/GHSA-9gwx-9cwp-5c2m · Vendor Advisory
• https://github.com/opencast/opencast · Note
• https://github.com/opencast/opencast/commit/16b0d641713fe31b8518fcf14fc5e4e815d81206 · Note
• https://t.me/cvenotify/16415 · Telegram Post
• https://t.me/cibsecurity/25476 · Telegram Post