What is CVE-2021-33503?

CVE-2021-33503 is a high-severity vulnerability in Oracle Enterprise Manager Ops Center, classified under Uncontrolled Resource Consumption. CVSS score: 7.5/10. Published 2021-06-29.

How severe is CVE-2021-33503?

High severity. CVSS v3 base score is 7.5 out of 10.

Is CVE-2021-33503 known to be exploited?

12 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Resource exhaustion in Oracle Enterprise Manager Ops Center

CVE-2021-33503

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.

Vulnerability class: DoS (Denial of Service)

Published 2021-06-29 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.033 (88.0th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 88th percentile — 88.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.033 · newest: 0.033 · change: 0.000

Affected products

Oracle Enterprise Manager Ops Center — versions 12.4.0.0
Oracle Instantis Enterprisetrack — versions 17.1, 17.2, 17.3
Oracle Zfs Storage Appliance Kit — versions 8.8
Python Urllib3
Fedoraproject Fedora — versions 33, 34

Weakness classification (CWE)

CWE-400 — Uncontrolled Resource Consumption

Public proof-of-concept exploits

References

lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/… (vendor-advisory)
lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/… (vendor-advisory)
security.gentoo.org/glsa/202107-36 (vendor-advisory, Third Party Advisory)
www.oracle.com/security-alerts/cpuoct2021.html (Patch, Third Party Advisory)
github.com/advisories/GHSA-q2q7-5pp4-w6pg (Third Party Advisory)
github.com/urllib3/urllib3/commit/2d4a3fee6de2fa45eb82169361918f759269b4ec (Patch, Third Party Advisory)

Frequently asked questions

What is CVE-2021-33503?: CVE-2021-33503 is a high-severity vulnerability in Oracle Enterprise Manager Ops Center, classified under Uncontrolled Resource Consumption. CVSS score: 7.5/10. Published 2021-06-29.
How severe is CVE-2021-33503?: High severity. CVSS v3 base score is 7.5 out of 10.
Is CVE-2021-33503 known to be exploited?: 12 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.