An issue was discovered in urllib3 before 1.26.5. When provided with a URL containing many @ characters in the authority component, the authority regular expression exhibits catastrophic backtracking, causing a denial of service if a URL were passed as a parameter or redirected to via an HTTP redirect.
Published 2021-06-29 11:15:08
Updated 2023-08-24 13:42:23
Source MITRE
View at NVD,   CVE.org
Vulnerability category: Denial of service

Exploit prediction scoring system (EPSS) score for CVE-2021-33503

Probability of exploitation activity in the next 30 days: 0.29%

Percentile, the proportion of vulnerabilities that are scored at or less: ~ 68 % EPSS Score History EPSS FAQ

CVSS scores for CVE-2021-33503

Base Score Base Severity CVSS Vector Exploitability Score Impact Score Score Source
5.0
MEDIUM AV:N/AC:L/Au:N/C:N/I:N/A:P
10.0
2.9
NIST
7.5
HIGH CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.9
3.6
NIST

CWE ids for CVE-2021-33503

  • The product does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources.
    Assigned by: nvd@nist.gov (Primary)

References for CVE-2021-33503

Products affected by CVE-2021-33503

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