CVE-2019-20104Public exploitNetwork attack vector

Unauthenticated service interruption via recursive XML expansion

Published Feb 6, 2020 · Updated Sep 16, 2024

XML entity expansion in Atlassian Crowd's OpenID client before 3.6.2 and in 3.7.0 allows remote attackers to interrupt service. The client parses attacker-supplied XML entity definitions without limiting recursive expansion, exhausting resources in the shared Tomcat container. The bundled testing application was deployed by default before 3.6.2 and shares Crowd's Tomcat process, so no authentication is required to affect availability.

CVSS severity7.5
High
EPSS probability2.43%
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 Atlassian Crowd's OpenID client before 3.6.2 and in 3.7.0 allows remote attackers to interrupt service. The client parses attacker-supplied XML entity definitions without limiting recursive expansion, exhausting resources in the shared Tomcat container. The bundled testing application was deployed by default before 3.6.2 and shares Crowd's Tomcat process, so no authentication is required to affect availability.

The record

CVE
CVE-2019-20104
Published
Feb 6, 2020
Updated
Sep 16, 2024
Vendor
Atlassian
Product
Crowd
Classifications
CWE-776, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 6, 2020CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 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=3.7.0 <unspecified
  2. Affected versionversion=unspecified <3.6.2
  3. Affected versionversion=unspecified <3.7.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Atlassian · Crowdversion=3.7.0 <unspecified; version=unspecified <3.6.2; version=unspecified <3.7.1

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.0NIST NVDAV:N/AC:L/Au:N/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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-776Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion')
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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