CVE-2021-36776: Github.com/rancher/rancher Rancher's Steve API Component Improper Vulnerability

HIGH
Advisory Identifier: GHSA-gvh9-xgrq-r8hw
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CVSS 8.8
CWE-284
Published
Advisory Summary

CVE-2021-36776 is a HIGH (CVSS 8.8) rancher's steve api component improper vulnerability (CWE-284: Improper Access Control) affecting Github.com/rancher/rancher libraries in the Go ecosystem. The issue involves rancher's steve api component improper authorization check allows privilege escalation. Remediation is available by upgrading affected packages to version 2.5.10.

CVE-2021-36776 at a Glance

CVE Identifier CVE-2021-36776
GHSA Identifier GHSA-gvh9-xgrq-r8hw
Severity HIGH
CVSS v3.1 Base Score 8.8
CWE Classification CWE-284: Improper Access Control
Affected Product Github.com/rancher/rancher
Package Ecosystem Go
Published Date
Last Updated

Security Impact

CVSS: 8.8

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required Low (PR:L)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity High (I:H)
Availability High (A:H)

How to Fix CVE-2021-36776

To remediate this vulnerability, upgrade all affected Github.com/rancher/rancher 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/rancher/rancher fixed: 2.5.10 
Upgrade github.com/rancher/rancher to 2.5.10
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/rancher/rancher

How to Check if You Are Affected

To determine whether your application is affected by CVE-2021-36776, inspect your project dependencies for Github.com/rancher/rancher:

inspect dependencies for github.com/rancher/rancher

Analyze the terminal output to locate any version of Github.com/rancher/rancher in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 2.5.10), 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-284: Improper Access Control, where the product does not restrict or incorrectly restricts access to a resource from an unauthorized actor. In Github.com/rancher/rancher, 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 A flaw discovered in Rancher versions from 2.5.0 up to and including 2.5.9 allows an authenticated user to impersonate any user on a cluster through the Steve API proxy, without requiring knowledge of the impersonated user's credentials. This is due to the Steve API proxy not dropping the impersonation header before sending the request to the Kubernetes API. A malicious user with authenticated access to Rancher could use this to impersonate another user with administrator access in Rancher, receiving, then, administrator level access in the cluster. ### Patches Patched versions include releases 2.5.10, 2.6.0 and later versions. ### Workarounds Limit access in Rancher to trusted users. There is not a direct mitigation besides upgrading to the patched Rancher versions. ### For more information If you have any questions or comments about this advisory: * Reach out to [SUSE Rancher Security team](https://github.com/rancher/rancher/security/policy) for security related inquiries. * Open an issue in [Rancher](https://github.com/rancher/rancher/issues/new/choose) repository. * Verify our [support matrix](https://www.suse.com/suse-rancher/support-matrix/all-supported-versions/) and [product support lifecycle](https://www.suse.com/lifecycle/).

CVE-2021-36776 Affected Github.com/rancher/rancher Versions

1 component(s)
Fixed Versions:
2.5.10
Product / Package Ecosystem Affected Versions Fixed Version
github.com/rancher/rancher
golang/github.com/rancher/rancher
Go
≥ 2.5.0
< 2.5.10
2.5.10

References

NVD — CVE-2021-36776 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-36776
bugzilla.suse.com/show_bug.cgi WEB
https://bugzilla.suse.com/show_bug.cgi?id=1189413
Github.com/rancher/rancher Source Repository REPOSITORY
https://github.com/rancher/rancher

Frequently Asked Questions

What is CVE-2021-36776?
CVE-2021-36776 is a security vulnerability in Github.com/rancher/rancher involving Rancher's Steve API Component Improper authorization check allows privilege escalation under CWE-284: Improper Access Control.
Which Github.com/rancher/rancher versions are affected?
Affected versions include releases prior to 2.5.10 across affected packages: github.com/rancher/rancher.
What version fixes CVE-2021-36776?
Upgrading to 2.5.10 (or the latest patched release for your respective branch) resolves the vulnerability.
Is github.com/rancher/rancher affected?
Yes, github.com/rancher/rancher is affected in releases prior to 2.5.10. Upgrade your dependency to 2.5.10 or later.
What is the CVSS score of CVE-2021-36776?
CVE-2021-36776 has a CVSS v3.1 base score of 8.8 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2021-36776?
CVE-2021-36776 is classified under CWE-284: Improper Access Control (The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor.).
How can I check Go dependencies for CVE-2021-36776?
Run the dependency tree command: 'inspect dependencies for github.com/rancher/rancher'. 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-gvh9-xgrq-r8hw",
  "modified" : "2024-07-08T20:42:19Z",
  "published" : "2024-04-24T21:01:53Z",
  "aliases" : [ "CVE-2021-36776" ],
  "summary" : "Rancher's Steve API Component Improper authorization check allows privilege escalation",
  "details" : "### Impact\n\nA flaw discovered in Rancher versions from 2.5.0 up to and including 2.5.9 allows an authenticated user to impersonate any user on a cluster through the Steve API proxy, without requiring knowledge of the impersonated user's credentials. This is due to the Steve API proxy not dropping the impersonation header before sending the request to the Kubernetes API. A malicious user with authenticated access to Rancher could use this to impersonate another user with administrator access in Rancher, receiving, then, administrator level access in the cluster.\n\n### Patches\nPatched versions include releases 2.5.10, 2.6.0 and later versions.\n\n### Workarounds\nLimit access in Rancher to trusted users. There is not a direct mitigation besides upgrading to the patched Rancher versions.\n\n### For more information\nIf you have any questions or comments about this advisory:\n* Reach out to [SUSE Rancher Security team](https://github.com/rancher/rancher/security/policy) for security related inquiries.\n* Open an issue in [Rancher](https://github.com/rancher/rancher/issues/new/choose) repository.\n* Verify our [support matrix](https://www.suse.com/suse-rancher/support-matrix/all-supported-versions/) and [product support lifecycle](https://www.suse.com/lifecycle/).",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/rancher/rancher"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.5.0"
      }, {
        "fixed" : "2.5.10"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 2.5.9"
    }
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-36776"
  }, {
    "type" : "WEB",
    "url" : "https://bugzilla.suse.com/show_bug.cgi?id=1189413"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/rancher/rancher"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-284" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2024-04-24T21:01:53Z",
    "nvd_published_at" : "2022-04-04T13:15:00Z"
  }
}