CVE-2021-41496: Numpy Buffer Copy Without Checking Size Vulnerability

MODERATE
Advisory Identifier: GHSA-f7c7-j99h-c22f
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CVSS 5.5
CWE-120
Published
Advisory Summary

CVE-2021-41496 is a MODERATE (CVSS 5.5) buffer copy without checking size vulnerability (CWE-120: Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')) affecting Numpy libraries in the PyPI ecosystem. The issue involves buffer copy without checking size of input in numpy. Remediation is available by upgrading affected packages to version 1.19.

CVE-2021-41496 at a Glance

CVE Identifier CVE-2021-41496
GHSA Identifier GHSA-f7c7-j99h-c22f
Severity MODERATE
CVSS v3.1 Base Score 5.5
CWE Classification CWE-120: Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
Affected Product Numpy
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 5.5

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

Attack Vector Local (AV:L)
Attack Complexity Low (AC:L)
Privileges Required Low (PR:L)
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-2021-41496

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

numpy fixed: 1.19 
pip install numpy>=1.19
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 numpy

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2021-41496, inspect your installed packages using pip:

pip show numpy

Analyze the terminal output to locate any version of Numpy in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.19), your application is affected.

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

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-120: Buffer Copy without Checking Size of Input ('Classic Buffer Overflow'), where the product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer. In Numpy, 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

Buffer overflow in the array_from_pyobj function of fortranobject.c in NumPy < 1.19, which allows attackers to conduct a Denial of Service attacks by carefully constructing an array with negative values.

CVE-2021-41496 Affected Numpy Versions

1 component(s)
Fixed Versions:
1.19
Product / Package Ecosystem Affected Versions Fixed Version
numpy
pypi/numpy
PyPI
< 1.19
1.19

References

NVD — CVE-2021-41496 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-41496
Numpy Source Repository REPOSITORY
https://github.com/numpy/numpy/issues/19000
Numpy Source Repository REPOSITORY
https://github.com/numpy/numpy
Numpy Security Information SECURITY
https://www.oracle.com/security-alerts/cpujul2022.html

Frequently Asked Questions

What is CVE-2021-41496?
CVE-2021-41496 is a security vulnerability in Numpy involving Buffer Copy without Checking Size of Input in NumPy under CWE-120: Buffer Copy without Checking Size of Input ('Classic Buffer Overflow').
Which Numpy versions are affected?
Affected versions include releases prior to 1.19 across affected packages: numpy.
What version fixes CVE-2021-41496?
Upgrading to 1.19 (or the latest patched release for your respective branch) resolves the vulnerability.
Is numpy affected?
Yes, numpy is affected in releases prior to 1.19. Upgrade your dependency to 1.19 or later.
What is the CVSS score of CVE-2021-41496?
CVE-2021-41496 has a CVSS v3.1 base score of 5.5 (MODERATE) with vector string CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2021-41496?
CVE-2021-41496 is classified under CWE-120: Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') (The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer.).
How can I check PyPI dependencies for CVE-2021-41496?
Run the dependency tree command: 'pip show numpy'. 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-f7c7-j99h-c22f",
  "modified" : "2022-06-21T20:09:56Z",
  "published" : "2022-02-08T00:00:56Z",
  "aliases" : [ "CVE-2021-41496" ],
  "summary" : "Buffer Copy without Checking Size of Input in NumPy",
  "details" : "Buffer overflow in the array_from_pyobj function of fortranobject.c in NumPy < 1.19, which allows attackers to conduct a Denial of Service attacks by carefully constructing an array with negative values.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "numpy"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.19"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 1.18.5"
    }
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-41496"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/numpy/numpy/issues/19000"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/numpy/numpy"
  }, {
    "type" : "WEB",
    "url" : "https://www.oracle.com/security-alerts/cpujul2022.html"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-120" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2022-06-21T20:09:56Z",
    "nvd_published_at" : "2021-12-17T20:15:00Z"
  }
}