CVE-2021-33503

Urllib3 vulnerability

CVSS

7.5

EPSS

3.2%

EPSS pct

87th

Exploited

No known

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.

Affected vendor

Python

Affected product

Urllib3

CVSS vector

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

Weakness type (CWE)

CWE-400 — Uncontrolled Resource Consumption

Published

2021-06-29

Risk analysis

Based on its CVSS vector, this vulnerability is exploitable over the network, low attack complexity, requiring no privileges, no user interaction. Successful exploitation leads to high impact to availability.

Its EPSS score of 3.2% reflects a lower probability of exploitation activity in the wild over the next 30 days, placing it above 87% of all scored CVEs.

Check your external exposure to CVE-2021-33503

Confirm whether Python Urllib3 is running on any internet-facing host or subdomain.
Match discovered service fingerprints against the version affected by CVE-2021-33503.
Prioritise remediation if the asset is public, business-critical, or near authentication/payment flows.

How ThreatPort helps with CVE-2021-33503

ThreatPort's external attack surface scanner checks your internet-facing assets — agentlessly, from the outside in — for the exposed services and versions that CVE-2021-33503 affects, then prioritises the finding by real risk using CISA KEV and FIRST.org EPSS.

Run a free external exposure scan

Are you exposed to CVE-2021-33503?

Run an instant, non-intrusive external scan to check your attack surface for CVE-2021-33503.

Start free scan

No credit card. Agentless.

Related vulnerabilities

HIGH

CVE-2015-3086

Flash Player vulnerability