CVE-2020-7212: Urllib3 Remote Code Execution Vulnerability

HIGH
Advisory Identifier: GHSA-hmv2-79q8-fv6g
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CVSS 7.5
CWE-400
Published
Advisory Summary

CVE-2020-7212 is a HIGH (CVSS 7.5) remote code execution vulnerability (CWE-400: Uncontrolled Resource Consumption) affecting Urllib3 libraries in the PyPI ecosystem. The issue involves uncontrolled resource consumption in urllib3. Remediation is available by upgrading affected packages to version 1.25.8.

CVE-2020-7212 at a Glance

CVE Identifier CVE-2020-7212
GHSA Identifier GHSA-hmv2-79q8-fv6g
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-400: Uncontrolled Resource Consumption
Affected Product Urllib3
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-2020-7212

To remediate this vulnerability, upgrade all affected Urllib3 dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

urllib3 fixed: 1.25.8 
pip install urllib3>=1.25.8
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 urllib3

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2020-7212, inspect your installed packages using pip:

pip show urllib3

Analyze the terminal output to locate any version of Urllib3 in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.25.8), your application is affected.

Note: The pip show urllib3 command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-400: Uncontrolled Resource Consumption, where the product does not properly control the allocation and maintenance of a limited resource. In Urllib3, 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

The _encode_invalid_chars function in util/url.py in the urllib3 library 1.25.2 through 1.25.7 for Python allows a denial of service (CPU consumption) because of an inefficient algorithm. The percent_encodings array contains all matches of percent encodings. It is not deduplicated. For a URL of length N, the size of percent_encodings may be up to O(N). The next step (normalize existing percent-encoded bytes) also takes up to O(N) for each step, so the total time is O(N^2). If percent_encodings were deduplicated, the time to compute _encode_invalid_chars would be O(kN), where k is at most 484 ((10+6*2)^2).

CVE-2020-7212 Affected Urllib3 Versions

1 component(s)
Fixed Versions:
1.25.8
Product / Package Ecosystem Affected Versions Fixed Version
urllib3
pypi/urllib3
PyPI
≥ 1.25.2
< 1.25.8
1.25.8

References

NVD — CVE-2020-7212 NVD
https://nvd.nist.gov/vuln/detail/CVE-2020-7212
Security Fix Commit FIX COMMIT
https://github.com/urllib3/urllib3/commit/a74c9cfbaed9f811e7563cfc3dce894928e0221a
GitHub Advisory / Wiki ADVISORY
https://github.com/advisories/GHSA-hmv2-79q8-fv6g
Urllib3 Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/urllib3/PYSEC-2020-149.yaml
Urllib3 Source Repository REPOSITORY
https://github.com/urllib3/urllib3
Urllib3 Source Repository REPOSITORY
https://github.com/urllib3/urllib3/blob/master/CHANGES.rst
pypi.org/project/urllib3/1.2... WEB
https://pypi.org/project/urllib3/1.25.8

Frequently Asked Questions

What is CVE-2020-7212?
CVE-2020-7212 is a security vulnerability in Urllib3 involving Uncontrolled Resource Consumption in urllib3 under CWE-400: Uncontrolled Resource Consumption.
Which Urllib3 versions are affected?
Affected versions include releases prior to 1.25.8 across affected packages: urllib3.
What version fixes CVE-2020-7212?
Upgrading to 1.25.8 (or the latest patched release for your respective branch) resolves the vulnerability.
Is urllib3 affected?
Yes, urllib3 is affected in releases prior to 1.25.8. Upgrade your dependency to 1.25.8 or later.
What is the CVSS score of CVE-2020-7212?
CVE-2020-7212 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-2020-7212?
CVE-2020-7212 is classified under CWE-400: Uncontrolled Resource Consumption (The product does not properly control the allocation and maintenance of a limited resource.).
How can I check PyPI dependencies for CVE-2020-7212?
Run the dependency tree command: 'pip show urllib3'. 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-hmv2-79q8-fv6g",
  "modified" : "2024-11-18T22:23:05Z",
  "published" : "2021-04-30T17:31:43Z",
  "aliases" : [ "CVE-2020-7212" ],
  "summary" : "Uncontrolled Resource Consumption in urllib3",
  "details" : "The _encode_invalid_chars function in util/url.py in the urllib3 library 1.25.2 through 1.25.7 for Python allows a denial of service (CPU consumption) because of an inefficient algorithm. The percent_encodings array contains all matches of percent encodings. It is not deduplicated. For a URL of length N, the size of percent_encodings may be up to O(N). The next step (normalize existing percent-encoded bytes) also takes up to O(N) for each step, so the total time is O(N^2). If percent_encodings were deduplicated, the time to compute _encode_invalid_chars would be O(kN), where k is at most 484 ((10+6*2)^2).",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "urllib3"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.25.2"
      }, {
        "fixed" : "1.25.8"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 1.25.7"
    }
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2020-7212"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/urllib3/urllib3/commit/a74c9cfbaed9f811e7563cfc3dce894928e0221a"
  }, {
    "type" : "ADVISORY",
    "url" : "https://github.com/advisories/GHSA-hmv2-79q8-fv6g"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/urllib3/PYSEC-2020-149.yaml"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/urllib3/urllib3"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/urllib3/urllib3/blob/master/CHANGES.rst"
  }, {
    "type" : "WEB",
    "url" : "https://pypi.org/project/urllib3/1.25.8"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-400" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-04-22T22:04:31Z",
    "nvd_published_at" : "2020-03-06T20:15:00Z"
  }
}