CVE-2021-28667: St2client StackStorm St2 Infinite Loop Condition Vulnerability

HIGH
Advisory Identifier: GHSA-39mj-fpg2-3jrg
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CVSS 7.5
CWE-835
Published
Advisory Summary

CVE-2021-28667 is a HIGH (CVSS 7.5) stackstorm st2 infinite loop condition vulnerability (CWE-835: Loop with Unreachable Exit Condition ('Infinite Loop')) affecting St2client libraries in the PyPI ecosystem. The issue involves stackstorm st2 infinite loop condition. Remediation is available by upgrading affected packages to version 3.4.1.

CVE-2021-28667 at a Glance

CVE Identifier CVE-2021-28667
GHSA Identifier GHSA-39mj-fpg2-3jrg
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-835: Loop with Unreachable Exit Condition ('Infinite Loop')
Affected Product St2client
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 7.5

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

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

How to Fix CVE-2021-28667

To remediate this vulnerability, upgrade all affected St2client dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

st2client fixed: 3.4.1 
pip install st2client>=3.4.1
Verify Direct and Transitive Dependencies

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

pip show st2client

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2021-28667, inspect your installed packages using pip:

pip show st2client

Analyze the terminal output to locate any version of St2client in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 3.4.1), your application is affected.

Note: The pip show st2client command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-835: Loop with Unreachable Exit Condition ('Infinite Loop'), where the product contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop. In St2client, 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

StackStorm before 3.4.1, in some situations, has an infinite loop that consumes all available memory and disk space. This can occur if Python 3.x is used, the locale is not utf-8, and there is an attempt to log Unicode data (from an action or rule name).

CVE-2021-28667 Affected St2client Versions

1 component(s)
Fixed Versions:
3.4.1
Product / Package Ecosystem Affected Versions Fixed Version
st2client
pypi/st2client
PyPI
< 3.4.1
3.4.1

References

NVD — CVE-2021-28667 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-28667
St2client Source Repository REPOSITORY
https://github.com/StackStorm/st2
St2client Security Information SECURITY
https://stackstorm.com/2021/03/10/stackstorm-v3-4-1-security-fix

Frequently Asked Questions

What is CVE-2021-28667?
CVE-2021-28667 is a security vulnerability in St2client involving StackStorm st2 Infinite Loop Condition under CWE-835: Loop with Unreachable Exit Condition ('Infinite Loop').
Which St2client versions are affected?
Affected versions include releases prior to 3.4.1 across affected packages: st2client.
What version fixes CVE-2021-28667?
Upgrading to 3.4.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is st2client affected?
Yes, st2client is affected in releases prior to 3.4.1. Upgrade your dependency to 3.4.1 or later.
What is the CVSS score of CVE-2021-28667?
CVE-2021-28667 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2021-28667?
CVE-2021-28667 is classified under CWE-835: Loop with Unreachable Exit Condition ('Infinite Loop') (The product contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop.).
How can I check PyPI dependencies for CVE-2021-28667?
Run the dependency tree command: 'pip show st2client'. 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-39mj-fpg2-3jrg",
  "modified" : "2023-08-07T20:56:50Z",
  "published" : "2022-05-24T17:44:46Z",
  "withdrawn" : "2023-08-07T20:56:50Z",
  "aliases" : [ "CVE-2021-28667" ],
  "summary" : "StackStorm st2 Infinite Loop Condition",
  "details" : "StackStorm before 3.4.1, in some situations, has an infinite loop that consumes all available memory and disk space. This can occur if Python 3.x is used, the locale is not utf-8, and there is an attempt to log Unicode data (from an action or rule name).",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "st2client"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.4.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-28667"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/StackStorm/st2"
  }, {
    "type" : "WEB",
    "url" : "https://stackstorm.com/2021/03/10/stackstorm-v3-4-1-security-fix"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-835" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2023-07-10T22:59:05Z",
    "nvd_published_at" : "2021-03-18T03:15:00Z"
  }
}