CVE-2020-26276: Github.com/fleetdm/fleet/v4 SAML Authentication Vulnerability Due To Vulnerability

HIGH
Advisory Identifier: GHSA-w3wf-cfx3-6gcx
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CWE-290
Published
Advisory Summary

CVE-2020-26276 is a HIGH saml authentication vulnerability due to vulnerability (CWE-290: Authentication Bypass by Spoofing) affecting Github.com/fleetdm/fleet/v4 libraries in the Go ecosystem. The issue involves saml authentication vulnerability due to stdlib xml parsing. Remediation is available by upgrading affected packages to version 3.5.1.

CVE-2020-26276 at a Glance

CVE Identifier CVE-2020-26276
GHSA Identifier GHSA-w3wf-cfx3-6gcx
Severity HIGH
CVSS v3.1 Base Score N/A
CWE Classification CWE-290: Authentication Bypass by Spoofing
Affected Product Github.com/fleetdm/fleet/v4
Package Ecosystem Go
Published Date
Last Updated

How to Fix CVE-2020-26276

To remediate this vulnerability, upgrade all affected Github.com/fleetdm/fleet/v4 dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

github.com/fleetdm/fleet/v4 fixed: 3.5.1 
Upgrade github.com/fleetdm/fleet/v4 to 3.5.1
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for github.com/fleetdm/fleet/v4

How to Check if You Are Affected

To determine whether your application is affected by CVE-2020-26276, inspect your project dependencies for Github.com/fleetdm/fleet/v4:

inspect dependencies for github.com/fleetdm/fleet/v4

Analyze the terminal output to locate any version of Github.com/fleetdm/fleet/v4 in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 3.5.1), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-290: Authentication Bypass by Spoofing, where this attack-focused weakness is caused by incorrectly implemented authentication schemes that are subject to spoofing attacks. In Github.com/fleetdm/fleet/v4, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Impact 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. ### Patches This issue is patched in 3.5.1 using https://github.com/mattermost/xml-roundtrip-validator. ### Workarounds If upgrade to 3.5.1 is not possible, users should disable SSO authentication in Fleet. ### References See https://mattermost.com/blog/coordinated-disclosure-go-xml-vulnerabilities/ for more information about the underlying vulnerabilities. ### For more information If you have any questions or comments about this advisory: * Email us at [security@fleetdm.com](mailto:security@fleetdm.com) * Join #fleet in [osquery Slack](https://join.slack.com/t/osquery/shared_invite/zt-h29zm0gk-s2DBtGUTW4CFel0f0IjTEw)

CVE-2020-26276 Affected Github.com/fleetdm/fleet/v4 Versions

1 component(s)
Fixed Versions:
3.5.1
Product / Package Ecosystem Affected Versions Fixed Version
github.com/fleetdm/fleet/v4
golang/github.com/fleetdm/fleet/v4
Go
< 3.5.1
3.5.1

References

GitHub Advisory / Wiki ADVISORY
https://github.com/fleetdm/fleet/security/advisories/GHSA-w3wf-cfx3-6gcx
NVD — CVE-2020-26276 NVD
https://nvd.nist.gov/vuln/detail/CVE-2020-26276
Security Fix Commit FIX COMMIT
https://github.com/fleetdm/fleet/commit/57812a532e5f749c8e18c6f6a652eca65c083607
Github.com/fleetdm/fleet/v4 Source Repository REPOSITORY
https://github.com/fleetdm/fleet/blob/master/CHANGELOG.md#fleet-351-dec-14-2020
Github.com/fleetdm/fleet/v4 Source Repository REPOSITORY
https://github.com/mattermost/xml-roundtrip-validator
mattermost.com/blog/coordinated-di... WEB
https://mattermost.com/blog/coordinated-disclosure-go-xml-vulnerabilities

Frequently Asked Questions

What is CVE-2020-26276?
CVE-2020-26276 is a security vulnerability in Github.com/fleetdm/fleet/v4 involving SAML authentication vulnerability due to stdlib XML parsing under CWE-290: Authentication Bypass by Spoofing.
Which Github.com/fleetdm/fleet/v4 versions are affected?
Affected versions include releases prior to 3.5.1 across affected packages: github.com/fleetdm/fleet/v4.
What version fixes CVE-2020-26276?
Upgrading to 3.5.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is github.com/fleetdm/fleet/v4 affected?
Yes, github.com/fleetdm/fleet/v4 is affected in releases prior to 3.5.1. Upgrade your dependency to 3.5.1 or later.
What CWE is associated with CVE-2020-26276?
CVE-2020-26276 is classified under CWE-290: Authentication Bypass by Spoofing (This attack-focused weakness is caused by incorrectly implemented authentication schemes that are subject to spoofing attacks.).
How can I check Go dependencies for CVE-2020-26276?
Run the dependency tree command: 'inspect dependencies for github.com/fleetdm/fleet/v4'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-w3wf-cfx3-6gcx",
  "modified" : "2022-02-11T23:59:14Z",
  "published" : "2022-02-11T23:59:14Z",
  "aliases" : [ "CVE-2020-26276" ],
  "summary" : "SAML authentication vulnerability due to stdlib XML parsing",
  "details" : "### Impact\nDue 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.\n\nUsers that configure Fleet with SSO login may be vulnerable to this issue.\n\n### Patches\nThis issue is patched in 3.5.1 using https://github.com/mattermost/xml-roundtrip-validator.\n\n### Workarounds\nIf upgrade to 3.5.1 is not possible, users should disable SSO authentication in Fleet.\n\n### References\nSee https://mattermost.com/blog/coordinated-disclosure-go-xml-vulnerabilities/ for more information about the underlying vulnerabilities.\n\n### For more information\nIf you have any questions or comments about this advisory:\n* Email us at [security@fleetdm.com](mailto:security@fleetdm.com)\n* Join #fleet in [osquery Slack](https://join.slack.com/t/osquery/shared_invite/zt-h29zm0gk-s2DBtGUTW4CFel0f0IjTEw)",
  "severity" : [ ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/fleetdm/fleet/v4"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.5.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/fleetdm/fleet/security/advisories/GHSA-w3wf-cfx3-6gcx"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2020-26276"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/fleetdm/fleet/commit/57812a532e5f749c8e18c6f6a652eca65c083607"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/fleetdm/fleet/blob/master/CHANGELOG.md#fleet-351-dec-14-2020"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mattermost/xml-roundtrip-validator"
  }, {
    "type" : "WEB",
    "url" : "https://mattermost.com/blog/coordinated-disclosure-go-xml-vulnerabilities"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-290" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-05-21T20:46:21Z",
    "nvd_published_at" : "2020-12-17T20:15:00Z"
  }
}