What’s Vulnerable › Vulnerabilities

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

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.3% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2021-06-16 · updated 2026-06-17
• Weakness: CWE-776

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.

Affected products

• opencast: before 9.6 — fixed in 9.6

How to fix

Upgrade to a fixed version: opencast 9.6. Check the vendor advisory for mitigations.

References

• https://github.com/opencast/opencast/commit/8ae27da5a6f658011a5741b3210e715b0dc6213e
• https://github.com/opencast/opencast/security/advisories/GHSA-9gwx-9cwp-5c2m
• https://github.com/opencast/opencast/commit/8ae27da5a6f658011a5741b3210e715b0dc6213e
• https://github.com/opencast/opencast/security/advisories/GHSA-9gwx-9cwp-5c2m

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