Is CVE-2021-42717 in the CISA KEV catalog?

No. CVE-2021-42717 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2021-42717?

CVE-2021-42717 has a CVSS v3 base score of 7.5 (HIGH).

What is the EPSS score for CVE-2021-42717?

CVE-2021-42717 has an EPSS score of 3.21% (87th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2021-42717?

Upgrade modsecurity on debian 12 to 3.0.6-1 or later. Fixes are available for 4 affected products.

CVE & CISA-KEV Catalog

CVE-2021-42717

HIGHEPSS 87th pctl

7.5

CVSS v3

NVD

Description

ModSecurity 3.x through 3.0.5 mishandles excessively nested JSON objects. Crafted JSON objects with nesting tens-of-thousands deep could result in the web server being unable to service legitimate requests. Even a moderately large (e.g., 300KB) HTTP request can occupy one of the limited NGINX worker processes for minutes and consume almost all of the available CPU on the machine. Modsecurity 2 is similarly vulnerable: the affected versions include 2.8.0 through 2.9.4.

CWE-674

How to fix

Remediation Available

modsecurityDebian

Fixed in:3.0.6-1CVE-2021-42717

libapache2-mod-security2Ubuntu

Fixed in:2.7.7-2ubuntu0.1~esm1USN-6370-1

Fixed in:2.9.0-1ubuntu0.1~esm1USN-6370-1

Fixed in:2.9.2-1ubuntu0.1~esm1USN-6370-1

Fixed in:2.9.3-1ubuntu0.1USN-6370-1

Fixed in:2.9.5-1ubuntu0.1~esm1USN-6370-1

libapache2-modsecurityUbuntu

Fixed in:2.7.7-2ubuntu0.1~esm1USN-6370-1

Fixed in:2.9.0-1ubuntu0.1~esm1USN-6370-1

modsecurity-apacheUbuntu

Fixed in:2.7.7-2ubuntu0.1~esm1USN-6370-1

Fixed in:2.9.0-1ubuntu0.1~esm1USN-6370-1

Fixed in:2.9.2-1ubuntu0.1~esm1USN-6370-1

Fixed in:2.9.3-1ubuntu0.1USN-6370-1

Fixed in:2.9.5-1ubuntu0.1~esm1USN-6370-1

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

3.21%probability of exploitation in 30 days

87thpercentile

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

References

Patch1

oracle.com

Exploit1

trustwave.com

Third-Party Advisory2

Embed a live status badge for CVE-2021-42717

Markdown

[![CVE-2021-42717](https://tridentstack.com/cve/badge/CVE-2021-42717.svg)](https://tridentstack.com/cve/CVE-2021-42717)

HTML

<a href="https://tridentstack.com/cve/CVE-2021-42717"><img src="https://tridentstack.com/cve/badge/CVE-2021-42717.svg" alt="CVE-2021-42717"></a>

Find and fix vulnerabilities across your fleet

TridentStack Control continuously scans your Windows, macOS, and Linux fleet for known vulnerabilities, prioritizes them by severity and active exploitation, and patches them automatically.

Start free

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 2025-07-03.