CVE-2020-26290
Critical security issues in XML encoding in Dex
Dex is a federated OpenID Connect provider written in Go. In Dex before version 2.27.0 there is a critical set of vulnerabilities which impacts users leveraging the SAML connector. The vulnerabilities enables potential signature bypass due to issues with XML encoding in the underlying Go library. The vulnerabilities have been addressed in version 2.27.0 by using the xml-roundtrip-validator from Mattermost (see related references).
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- Required
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
9.3
Critical security issues in XML encoding in Dex
Dex is a federated OpenID Connect provider written in Go. In Dex before version 2.27.0 there is a critical set of vulnerabilities which impacts users leveraging the SAML connector. The vulnerabilities enables potential signature bypass due to issues with XML encoding in the underlying Go library. The vulnerabilities have been addressed in version 2.27.0 by using the xml-roundtrip-validator from Mattermost (see related references).
- Record
CVE-2020-26290- CVSS 3.1
- 9.3 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N - Weakness
- CWE-347
- Updated
- 2026-11-02
EUVDEUVD-2021-2551
9.3
Dex is a federated OpenID Connect provider written in Go. In Dex before version 2.27.0 there is a critical set of vulnerabilities which impacts users leveraging the SAML connector. The vulnerabilities enables potential signature bypass due to issues with XML encoding in the underlying Go library. The vulnerabilities have been addressed in version 2.27.0 by using the xml-roundtrip-validator from Mattermost (see related references).
- Record
EUVD-2021-2551- CVSS 3.1
- 9.3 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N - Updated
- 2026-11-03
GitHub AdvisoriesGHSA-m9hp-7r99-94h5
9.3
Critical security issues in XML encoding in github.com/dexidp/dex
Impact
The following vulnerabilities have been disclosed, which impact users leveraging the SAML connector:
Signature Validation Bypass (CVE-2020-15216): https://github.com/russellhaering/goxmldsig/security/advisories/GHSA-q547-gmf8-8jr7
encoding/xml instabilities:
- Element namespace prefix instability (CVE-2020-29511)
- Attribute namespace prefix instability (CVE-2020-29509)
- Directive comment instability (CVE-2020-29510)
Patches
Immediately update to Dex v2.27.0.
Workarounds
There are no known workarounds.
- Record
GHSA-m9hp-7r99-94h5- CVSS 3.1
- 9.3 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N - Weakness
- CWE-347
- Updated
- 2026-11-02
NVD
9.3
Dex is a federated OpenID Connect provider written in Go. In Dex before version 2.27.0 there is a critical set of vulnerabilities which impacts users leveraging the SAML connector. The vulnerabilities enables potential signature bypass due to issues with XML encoding in the underlying Go library. The vulnerabilities have been addressed in version 2.27.0 by using the xml-roundtrip-validator from Mattermost (see related references).
- Record
CVE-2020-26290- CVSS 3.1
- 9.3 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N - CVSS 3.1
- 9.6 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H - CVSS 2.0
- 6.8 Medium
AV:N/AC:M/Au:N/C:P/I:P/A:P - Weakness
- CWE-347
- Updated
- 2026-11-02
OSV
9.6
Dex is a federated OpenID Connect provider written in Go. In Dex before version 2.27.0 there is a critical set of vulnerabilities which impacts users leveraging the SAML connector. The vulnerabilities enables potential signature bypass due to issues with XML encoding in the underlying Go library. The vulnerabilities have been addressed in version 2.27.0 by using the xml-roundtrip-validator from Mattermost (see related references).
- Record
CVE-2020-26290- CVSS 3.1
- 9.6 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H - Updated
- 2026-11-02
OSVCVE-2020-27847
9.8
A vulnerability exists in the SAML connector of the github.com/dexidp/dex library used to process SAML Signature Validation. This flaw allows an attacker to bypass SAML authentication. The highest threat from this vulnerability is to confidentiality, integrity, as well as system availability. This flaw affects dex versions before 2.27.0.
- Record
CVE-2020-27847- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-02
OSVGHSA-2x32-jm95-2cpx
9.8
Authentication Bypass in dex
A vulnerability exists in the SAML connector of the github.com/dexidp/dex library used to process SAML Signature Validation. This flaw allows an attacker to bypass SAML authentication. The highest threat from this vulnerability is to confidentiality, integrity, as well as system availability. This flaw affects dex versions before 2.27.0.
- Record
GHSA-2x32-jm95-2cpx- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-228, CWE-290
- Updated
- 2026-11-02
OSVGHSA-m9hp-7r99-94h5
9.3
Critical security issues in XML encoding in github.com/dexidp/dex
Impact
The following vulnerabilities have been disclosed, which impact users leveraging the SAML connector:
Signature Validation Bypass (CVE-2020-15216): https://github.com/russellhaering/goxmldsig/security/advisories/GHSA-q547-gmf8-8jr7
encoding/xml instabilities:
- Element namespace prefix instability (CVE-2020-29511)
- Attribute namespace prefix instability (CVE-2020-29509)
- Directive comment instability (CVE-2020-29510)
Patches
Immediately update to Dex v2.27.0.
Workarounds
There are no known workarounds.
- Record
GHSA-m9hp-7r99-94h5- CVSS 3.1
- 9.3 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N - Weakness
- CWE-347
- Updated
- 2026-11-02
OSVopenSUSE-SU-2024:10714-1 No score
dex-oidc-2.28.1-1.3 on GA media
These are all security issues fixed in the dex-oidc-2.28.1-1.3 package on the GA media of openSUSE Tumbleweed.
- Record
openSUSE-SU-2024:10714-1- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
github.com/dexidp/dexGo |
before 2.27.0 | 2.27.0 |
github.com/russellhaering/goxmldsigGo |
before 1.1.0 | 1.1.0 |
github.com/dexidp/dexGo From an advisory covering 2 CVEs |
before 2.27.0 | 2.27.0 |
github.com/russellhaering/goxmldsigGo From an advisory covering 2 CVEs |
before 1.1.0 | 1.1.0 |
dex-oidcopenSUSE:Tumbleweed |
before 2.28.1-1.3 | 2.28.1-1.3 |
History
| Recorded | Changed | Sources |
|---|---|---|
| affected, facts | ||
| aliases, products | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2020-26290 is a critical vulnerability (CVSS 9.3) in Dexidp Dex, published December 28, 2020. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.99%, the 62nd percentile. Fixed in github.com/dexidp/dex 2.27.0.
References
github.com/mattermost/xml-roundtrip-validator/blob/master/advisories/unstable-directives.md
github.com/mattermost/xml-roundtrip-validator/blob/master/advisories/unstable-elements.md
github.com/mattermost/xml-roundtrip-validator/blob/master/advisories/unstable-attributes.md
mattermost.com/blog/coordinated-disclosure-go-xml-vulnerabilities
github.com/dexidp/dex/security/advisories/GHSA-m9hp-7r99-94h5
github.com/russellhaering/goxmldsig/security/advisories/GHSA-q547-gmf8-8jr7
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github.com/dexidp/dex/commit/324b1c886b407594196113a3dbddebe38eecd4e8
github.com/dexidp/dex/releases/tag/v2.27.0
nvd.nist.gov/vuln/detail/CVE-2020-26290
github.com/russellhaering/goxmldsig/commit/f6188febf0c29d7ffe26a0436212b19cb9615e64
pkg.go.dev/vuln/GO-2020-0050
github.com/advisories/GHSA-m9hp-7r99-94h5
bugzilla.redhat.com/show_bug.cgi?id=1907732
nvd.nist.gov/vuln/detail/CVE-2020-27847
suse.com/security/cve/CVE-2020-26290