CVE-2021-27736
FusionAuth fusionauth-samlv2 before 0.5.4 allows XXE attacks via a forged AuthnRequest or...
FusionAuth fusionauth-samlv2 before 0.5.4 allows XXE attacks via a forged AuthnRequest or LogoutRequest because parseFromBytes uses javax.xml.parsers.DocumentBuilderFactory unsafely.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- Low
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- None
- Availability
- None
Exploit likelihood
What each source reports
NVD Score used
FusionAuth fusionauth-samlv2 before 0.5.4 allows XXE attacks via a forged AuthnRequest or LogoutRequest because parseFromBytes uses javax.xml.parsers.DocumentBuilderFactory unsafely.
- Record
CVE-2021-27736- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N - CVSS 2.0
- 4.0 Medium
AV:N/AC:L/Au:S/C:P/I:N/A:N - Weakness
- CWE-611
- Updated
- 2026-11-02
CVE List No score
FusionAuth fusionauth-samlv2 before 0.5.4 allows XXE attacks via a forged AuthnRequest or LogoutRequest because parseFromBytes uses javax.xml.parsers.DocumentBuilderFactory unsafely.
- Record
CVE-2021-27736- Updated
- 2026-11-02
EUVDEUVD-2021-14478 No score
FusionAuth fusionauth-samlv2 before 0.5.4 allows XXE attacks via a forged AuthnRequest or LogoutRequest because parseFromBytes uses javax.xml.parsers.DocumentBuilderFactory unsafely.
- Record
EUVD-2021-14478- Updated
- 2026-11-03
GitHub AdvisoriesGHSA-3jw3-99x8-h6xc No score
FusionAuth fusionauth-samlv2 before 0.5.4 allows XXE attacks via a forged AuthnRequest or...
FusionAuth fusionauth-samlv2 before 0.5.4 allows XXE attacks via a forged AuthnRequest or LogoutRequest because parseFromBytes uses javax.xml.parsers.DocumentBuilderFactory unsafely.
- Record
GHSA-3jw3-99x8-h6xc- Weakness
- CWE-611
- Updated
- 2026-11-02
OSV
FusionAuth fusionauth-samlv2 before 0.5.4 allows XXE attacks via a forged AuthnRequest or LogoutRequest because parseFromBytes uses javax.xml.parsers.DocumentBuilderFactory unsafely.
- Record
CVE-2021-27736- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N - Updated
- 2026-11-02
Affected products
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-27736 is a medium vulnerability (CVSS 6.5) in Fusionauth Saml V2, published April 22, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.32%, the 70th percentile. No source names a fixed version.
References
github.com/FusionAuth/fusionauth-samlv2/compare/0.5.3...0.5.4
compass-security.com/fileadmin/Research/Advisories/2021-03_CSNC-2021-004_FusionAuth_SAML_Library_XML_External_Entity.txt
nvd.nist.gov/vuln/detail/CVE-2021-27736