CVE-2021-31999: Github.com/rancher/rancher Rancher Privilege Escalation Vulnerability Vulnerability

HIGH
Advisory Identifier: GHSA-pvxj-25m6-7vqr
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CVSS 8.8
CWE-807
Published
Advisory Summary

CVE-2021-31999 is a HIGH (CVSS 8.8) rancher privilege escalation vulnerability vulnerability (CWE-807: Reliance on Untrusted Inputs in a Security Decision) affecting Github.com/rancher/rancher libraries in the Go ecosystem. The issue involves rancher privilege escalation vulnerability via malicious "connection" header. Remediation is available by upgrading affected packages to version 2.4.16, 2.5.9.

CVE-2021-31999 at a Glance

CVE Identifier CVE-2021-31999
GHSA Identifier GHSA-pvxj-25m6-7vqr
Severity HIGH
CVSS v3.1 Base Score 8.8
CWE Classification CWE-807: Reliance on Untrusted Inputs in a Security Decision
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-2021-31999

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: 2.4.16 
Upgrade github.com/rancher/rancher to 2.4.16
github.com/rancher/rancher fixed: 2.5.9 
Upgrade github.com/rancher/rancher to 2.5.9
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-2021-31999, 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 2.4.16), 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-807: Reliance on Untrusted Inputs in a Security Decision, where the product uses a protection mechanism that relies on the existence or values of an input, but the input can be modified by an untrusted actor in a way that bypasses the protection mechanism. 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

A vulnerability was discovered in Rancher 2.0.0 through the aforementioned patched versions, where a malicious Rancher user could craft an API request directed at the proxy for the Kubernetes API of a managed cluster to gain access to information they do not have access to. This is done by passing the "Impersonate-User" or "Impersonate-Group" header in the Connection header, which is then correctly removed by the proxy. At this point, instead of impersonating the user and their permissions, the request will act as if it was from the Rancher management server and incorrectly return the information. The vulnerability is limited to valid Rancher users with some level of permissions on the cluster. There is not a direct mitigation besides upgrading to the patched Rancher versions.

CVE-2021-31999 Affected Github.com/rancher/rancher Versions

2 component(s)
Fixed Versions:
2.4.162.5.9
Product / Package Ecosystem Affected Versions Fixed Version
github.com/rancher/rancher
golang/github.com/rancher/rancher
Go
≥ 2.0.0
< 2.4.16
2.4.16
github.com/rancher/rancher
golang/github.com/rancher/rancher
Go
≥ 2.5.0
< 2.5.9
2.5.9

References

NVD — CVE-2021-31999 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-31999
bugzilla.suse.com/show_bug.cgi WEB
https://bugzilla.suse.com/show_bug.cgi?id=1187084
Github.com/rancher/rancher Source Repository REPOSITORY
https://github.com/rancher/rancher
pkg.go.dev/vuln/go-2024-2778 WEB
https://pkg.go.dev/vuln/GO-2024-2778

Frequently Asked Questions

What is CVE-2021-31999?
CVE-2021-31999 is a security vulnerability in Github.com/rancher/rancher involving Rancher Privilege escalation vulnerability via malicious "Connection" header under CWE-807: Reliance on Untrusted Inputs in a Security Decision.
Which Github.com/rancher/rancher versions are affected?
Affected versions include releases prior to 2.4.16, 2.5.9 across affected packages: github.com/rancher/rancher.
What version fixes CVE-2021-31999?
Upgrading to 2.4.16, 2.5.9 (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 2.4.16, 2.5.9. Upgrade your dependency to 2.4.16, 2.5.9 or later.
What is the CVSS score of CVE-2021-31999?
CVE-2021-31999 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-2021-31999?
CVE-2021-31999 is classified under CWE-807: Reliance on Untrusted Inputs in a Security Decision (The product uses a protection mechanism that relies on the existence or values of an input, but the input can be modified by an untrusted actor in a way that bypasses the protection mechanism.).
How can I check Go dependencies for CVE-2021-31999?
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-pvxj-25m6-7vqr",
  "modified" : "2024-07-08T20:41:59Z",
  "published" : "2024-04-24T21:01:59Z",
  "aliases" : [ "CVE-2021-31999" ],
  "summary" : "Rancher Privilege escalation vulnerability via malicious \"Connection\" header",
  "details" : "A vulnerability was discovered in Rancher 2.0.0 through the aforementioned patched versions, where a malicious Rancher user could craft an API request directed at the proxy for the Kubernetes API of a managed cluster to gain access to information they do not have access to. This is done by passing the \"Impersonate-User\" or \"Impersonate-Group\" header in the Connection header, which is then correctly removed by the proxy. At this point, instead of impersonating the user and their permissions, the request will act as if it was from the Rancher management server and incorrectly return the information. The vulnerability is limited to valid Rancher users with some level of permissions on the cluster. There is not a direct mitigation besides upgrading to the patched Rancher versions. \n",
  "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" : "2.0.0"
      }, {
        "fixed" : "2.4.16"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/rancher/rancher"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.5.0"
      }, {
        "fixed" : "2.5.9"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-31999"
  }, {
    "type" : "WEB",
    "url" : "https://bugzilla.suse.com/show_bug.cgi?id=1187084"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/rancher/rancher"
  }, {
    "type" : "WEB",
    "url" : "https://pkg.go.dev/vuln/GO-2024-2778"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-807" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2024-04-24T21:01:59Z",
    "nvd_published_at" : "2021-07-15T09:15:00Z"
  }
}