Is CVE-2021-33503 in the CISA KEV catalog?

No. CVE-2021-33503 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2021-33503?

CVE-2021-33503 has a CVSS v3 base score of 7.5 (HIGH).

What is the EPSS score for CVE-2021-33503?

CVE-2021-33503 has an EPSS score of 3.27% (87th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2021-33503?

Upgrade python-urllib3 on debian 11 to 1.26.5-1~exp1 or later. Fixes are available for 3 affected products.

CVE & CISA-KEV Catalog

CVE-2021-33503

HIGHEPSS 87th pctl

7.5

CVSS v3

NVD

Description

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.

CWE-400Resource Exhaustion

How to fix

Remediation Available

python-urllib3Debian

Fixed in:1.26.5-1~exp1CVE-2021-33503

python-urllib3Ubuntu

Fixed in:1.25.8-2ubuntu0.2USN-5812-1

python3-urllib3Ubuntu

Fixed in:1.25.8-2ubuntu0.2USN-5812-1

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityNone

AvailabilityHigh

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

Exploit Intelligence

3.27%probability of exploitation in 30 days

87thpercentile

Elevated risk: more likely to be exploited than 87% of all known CVEs.

References

Patch2

Third-Party Advisory2

Other references2

Related Vulnerabilities

Other CWE-400 (Resource Exhaustion) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2023-44487	High	7.5	100%	KEV	Fix
CVE-2021-44228	Critical	10.0	100%	KEV + Ransom	Fix
CVE-2011-3192	High	7.8	99%	-	Fix
CVE-2019-11478	Medium	5.3	95%	-	Fix
CVE-2024-25617	Medium	5.3	89%	-	Fix
CVE-2018-1000115	High	7.5	89%	-	Fix

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2024-11-21.