Is CVE-2021-42013 in the CISA KEV catalog?

Yes. CVE-2021-42013 is on the CISA Known Exploited Vulnerabilities list, added 2021-11-03, and has known ransomware campaign use.

What is the CVSS severity of CVE-2021-42013?

CVE-2021-42013 has a CVSS v3 base score of 9.8 (CRITICAL).

What is the EPSS score for CVE-2021-42013?

CVE-2021-42013 has an EPSS score of 99.96% (100th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2021-42013?

Upgrade apache2 on debian 12 to 2.4.51-1 or later.

CVE & CISA-KEV Catalog

CVE-2021-42013

CRITICALCISA KEVEPSS 100th pctl

9.8

CVSS v3

NVD

Description

It was found that the fix for CVE-2021-41773 in Apache HTTP Server 2.4.50 was insufficient. An attacker could use a path traversal attack to map URLs to files outside the directories configured by Alias-like directives. If files outside of these directories are not protected by the usual default configuration "require all denied", these requests can succeed. If CGI scripts are also enabled for these aliased pathes, this could allow for remote code execution. This issue only affects Apache 2.4.49 and Apache 2.4.50 and not earlier versions.

CWE-22Path Traversal

How to fix

Remediation Available

apache2Debian

Fixed in:2.4.51-1CVE-2021-42013

TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works

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

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

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

Exploit Intelligence

99.96%probability of exploitation in 30 days

100thpercentile

Very high risk: more likely to be exploited than 100% of all known CVEs.

Known Exploited Vulnerability (CISA KEV)

Apache HTTP Server Path Traversal Vulnerability

Apache HTTP Server contains a path traversal vulnerability that allows an attacker to perform remote code execution if files outside directories configured by Alias-like directives are not under default require all denied or if CGI scripts are enabled. This CVE ID resolves an incomplete patch for CVE-2021-41773.

Apply updates per vendor instructions.

Remediation due: 2021-11-17

Associated with ransomware campaigns

References

Patch3

Exploit6

Vendor Advisory1

httpd.apache.org

Third-Party Advisory16

Government Resource1

cisa.gov

Mailing List2

Release Notes2

Related Vulnerabilities

Other CWE-22 (Path Traversal) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2024-23897	Critical	9.8	100%	KEV + Ransom	Fix
CVE-2023-32315	High	8.6	100%	KEV	Fix
CVE-2022-29464	Critical	9.8	100%	KEV + Ransom	-
CVE-2021-26086	Medium	5.3	100%	KEV	Fix
CVE-2021-22005	Critical	9.8	100%	KEV + Ransom	Fix
CVE-2020-5902	Critical	9.8	100%	KEV + Ransom	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 2025-10-27.