CVE-2020-26276 json
SAML authentication vulnerability in Fleet
published 2020-12-17 5 y ago modified 2026-09-10 1 mo ago also GHSA-w3wf-cfx3-6gcx , EUVD-2022-1220
- cvss
- 10.0
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 2.2%
- EPSS 2.2% chance of exploitation in 30 days, percentile 82%
- public exploits
- 0
- none known
Summary
Fleet is an open source osquery manager. In Fleet before version 3.5.1, due to issues in Go's standard library XML parsing, a valid SAML response may be mutated by an attacker to modify the trusted document. This can result in allowing unverified logins from a SAML IdP. Users that configure Fleet with SSO login may be vulnerable to this issue. This issue is patched in 3.5.1. The fix was made using https://github.com/mattermost/xml-roundtrip-validator If upgrade to 3.5.1 is not possible, users should disable SSO authentication in Fleet.
Patch / fix
Exploit prediction
2.20% chance of exploitation in the next 30 days, higher than 82% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 10.0 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H |
| NVD | 3.1 | 9.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
| NVD | 2.0 | 6.8 | AV:N/AC:M/Au:N/C:P/I:P/A:P |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| go | github.com/fleetdm/fleet/v4 | <3.5.1 |
3.5.1 |
Affected products
- fleetdm fleet
Classification
- Weakness
-
- CWE-290 Authentication Bypass by Spoofing
References
-
github.com
/fleetdm/fleet/commit/57812a532e5f749c8e18c6f6a652eca65c083607
web, patch, third-party-advisory
-
github.com
/fleetdm/fleet/security/advisories/GHSA-w3wf-cfx3-6gcx
web, third-party-advisory
-
github.com
/fleetdm/fleet/blob/master/CHANGELOG.md#fleet-351-dec-14-2020
web, release-notes, third-party-advisory
-
github.com
/mattermost/xml-roundtrip-validator
web, third-party-advisory
-
mattermost.com
/blog/coordinated-disclosure-go-xml-vulnerabilities
web, not-applicable, third-party-advisory
-
nvd.nist.gov
/vuln/detail/CVE-2020-26276
advisory
Sources
- CVE List CVE-2020-26276
- GitHub Advisory GHSA-w3wf-cfx3-6gcx
- NVD CVE-2020-26276
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