What’s Vulnerable › Vulnerabilities

CVE-2021-27736

• 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: 2021-04-22 · updated 2026-06-17
• Weakness: CWE-611

Description

FusionAuth fusionauth-samlv2 before 0.5.4 allows XXE attacks via a forged AuthnRequest or LogoutRequest because parseFromBytes uses javax.xml.parsers.DocumentBuilderFactory unsafely.

Affected products

• Fusionauth Saml V2: before 0.5.4 — fixed in 0.5.4

How to fix

Upgrade to a fixed version: Fusionauth Saml V2 0.5.4. Check the vendor advisory for mitigations.

References

• https://github.com/FusionAuth/fusionauth-samlv2/commit/c66fb689d50010662f705d5b585c6388ce555dbd
• https://github.com/FusionAuth/fusionauth-samlv2/compare/0.5.3...0.5.4
• https://www.compass-security.com/fileadmin/Research/Advisories/2021-03_CSNC-2021-004_FusionAuth_SAML_Library_XML_External_Entity.txt
• https://github.com/FusionAuth/fusionauth-samlv2/commit/c66fb689d50010662f705d5b585c6388ce555dbd
• https://github.com/FusionAuth/fusionauth-samlv2/compare/0.5.3...0.5.4
• https://www.compass-security.com/fileadmin/Research/Advisories/2021-03_CSNC-2021-004_FusionAuth_SAML_Library_XML_External_Entity.txt

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