CVE-2020-7212 Information

Description

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).

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Reference

https://github.com/urllib3/urllib3/blob/master/CHANGES.rst https://github.com/urllib3/urllib3/blob/master/CHANGES.rst https://github.com/urllib3/urllib3/commit/a74c9cfbaed9f811e7563cfc3dce894928e0221a https://github.com/urllib3/urllib3/commit/a74c9cfbaed9f811e7563cfc3dce894928e0221a https://pypi.org/project/urllib3/1.25.8/ https://pypi.org/project/urllib3/1.25.8/ 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+62)^2). cpe:2.3:a:python:urllib3::::::::*

Attack Complexity

LOW

Privileges Required

NONE

User Interaction Required

NONE

Scope

NONE

Confidentiality Impact

UNCHANGED

Integrity Impact

NONE

Availability Impact

NONE

Base Score

HIGH

Base Severity

7.5