Vulnerability CVE-2020-7212


Published: 2020-03-06

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).

Type:

CWE-400

(Uncontrolled Resource Consumption ('Resource Exhaustion'))

CVSS2 => (AV:N/AC:L/Au:N/C:N/I:N/A:C)

CVSS Base Score
Impact Subscore
Exploitability Subscore
7.8/10
6.9/10
10/10
Exploit range
Attack complexity
Authentication
Remote
Low
No required
Confidentiality impact
Integrity impact
Availability impact
None
None
Complete
Affected software
Python -> Urllib3 

 References:
https://github.com/urllib3/urllib3/blob/master/CHANGES.rst
https://github.com/urllib3/urllib3/commit/a74c9cfbaed9f811e7563cfc3dce894928e0221a
https://pypi.org/project/urllib3/1.25.8/

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