CVE-2021-23727: Celery OS Command Injection Vulnerability

HIGH
Advisory Identifier: GHSA-q4xr-rc97-m4xx
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CVSS 7.5
CWE-78 CWE-77
Published
Advisory Summary

CVE-2021-23727 is a HIGH (CVSS 7.5) os command injection vulnerability (CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')) affecting Celery libraries in the PyPI ecosystem. The issue involves os command injection in celery. Remediation is available by upgrading affected packages to version 5.2.2.

CVE-2021-23727 at a Glance

CVE Identifier CVE-2021-23727
GHSA Identifier GHSA-q4xr-rc97-m4xx
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
Affected Product Celery
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:H/PR:L/UI:N/S:U/C:H/I:H/A:H).

Attack Vector Network (AV:N)
Attack Complexity High (AC:H)
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-2021-23727

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

celery fixed: 5.2.2 
pip install celery>=5.2.2
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 celery

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2021-23727, inspect your installed packages using pip:

pip show celery

Analyze the terminal output to locate any version of Celery in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 5.2.2), your application is affected.

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

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection'), where the product constructs all or part of an os command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended os command when it is sent to a downstream component. In Celery, 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

This affects the package celery before 5.2.2. It by default trusts the messages and metadata stored in backends (result stores). When reading task metadata from the backend, the data is deserialized. Given that an attacker can gain access to, or somehow manipulate the metadata within a celery backend, they could trigger a stored command injection vulnerability and potentially gain further access to the system.

CVE-2021-23727 Affected Celery Versions

1 component(s)
Fixed Versions:
5.2.2
Product / Package Ecosystem Affected Versions Fixed Version
celery
pypi/celery
PyPI
< 5.2.2
5.2.2

References

NVD — CVE-2021-23727 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-23727
Security Fix Commit FIX COMMIT
https://github.com/celery/celery/commit/1f7ad7e6df1e02039b6ab9eec617d283598cad6b
GitHub Advisory / Wiki ADVISORY
https://github.com/advisories/GHSA-q4xr-rc97-m4xx
Celery Source Repository REPOSITORY
https://github.com/celery/celery
Celery Source Repository REPOSITORY
https://github.com/celery/celery/blob/master/Changelog.rst%23522
Celery Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/celery/PYSEC-2021-858.yaml
lists.fedoraproject.org/archives/list/packa... WEB
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/SYXRGHWHD2WWMHBWCVD5ULVINPKNY3P5
snyk.io/vuln/snyk-python-ce... WEB
https://snyk.io/vuln/SNYK-PYTHON-CELERY-2314953

Frequently Asked Questions

What is CVE-2021-23727?
CVE-2021-23727 is a security vulnerability in Celery involving OS Command Injection in celery under CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection').
Which Celery versions are affected?
Affected versions include releases prior to 5.2.2 across affected packages: celery.
What version fixes CVE-2021-23727?
Upgrading to 5.2.2 (or the latest patched release for your respective branch) resolves the vulnerability.
Is celery affected?
Yes, celery is affected in releases prior to 5.2.2. Upgrade your dependency to 5.2.2 or later.
What is the CVSS score of CVE-2021-23727?
CVE-2021-23727 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2021-23727?
CVE-2021-23727 is classified under CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection') (The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component.).
How can I check PyPI dependencies for CVE-2021-23727?
Run the dependency tree command: 'pip show celery'. 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-q4xr-rc97-m4xx",
  "modified" : "2024-09-06T16:27:25Z",
  "published" : "2022-01-06T22:22:02Z",
  "aliases" : [ "CVE-2021-23727" ],
  "summary" : "OS Command Injection in celery",
  "details" : "This affects the package celery before 5.2.2. It by default trusts the messages and metadata stored in backends (result stores). When reading task metadata from the backend, the data is deserialized. Given that an attacker can gain access to, or somehow manipulate the metadata within a celery backend, they could trigger a stored command injection vulnerability and potentially gain further access to the system.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:H/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "celery"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "5.2.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-23727"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/celery/celery/commit/1f7ad7e6df1e02039b6ab9eec617d283598cad6b"
  }, {
    "type" : "ADVISORY",
    "url" : "https://github.com/advisories/GHSA-q4xr-rc97-m4xx"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/celery/celery"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/celery/celery/blob/master/Changelog.rst%23522"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/celery/PYSEC-2021-858.yaml"
  }, {
    "type" : "WEB",
    "url" : "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/SYXRGHWHD2WWMHBWCVD5ULVINPKNY3P5"
  }, {
    "type" : "WEB",
    "url" : "https://snyk.io/vuln/SNYK-PYTHON-CELERY-2314953"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-77", "CWE-78" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2022-01-06T19:17:52Z",
    "nvd_published_at" : "2021-12-29T17:15:00Z"
  }
}