CVE-2021-32623Network attack vector

Denial of service via recursive XML entity expansion

Published Jun 15, 2021 · Updated Aug 3, 2024

XML entity expansion in Opencast before 9.6 allows remote authenticated users to cause denial of service via a crafted ingest request. The ingestdownload endpoint parses createMediaPackage.xml and expands recursively defined entities, consuming very large amounts of memory before processing completes. Ingest privileges are required, and a single request can take down the service without disclosing data; the vendor reports no workaround.

CVSS severity8.1
High
EPSS probability1.25%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

XML entity expansion in Opencast before 9.6 allows remote authenticated users to cause denial of service via a crafted ingest request. The ingestdownload endpoint parses createMediaPackage.xml and expands recursively defined entities, consuming very large amounts of memory before processing completes. Ingest privileges are required, and a single request can take down the service without disclosing data; the vendor reports no workaround.

The record

CVE
CVE-2021-32623
Published
Jun 15, 2021
Updated
Aug 3, 2024
Vendor
Opencast
Product
Opencast
Classifications
CWE-776, T1499.003
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 15, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 9.6

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Opencast · Opencastversion=< 9.6

Published CVSS scores

8.1NISTCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H
4.0NISTAV:N/AC:L/Au:S/C:N/I:N/A:P

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-776Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion')
T1499.003Application Exhaustion

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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