TI-2021-18927 Aliases CVE-2021-42717 GHSA-w3vf-7fpc-9fww

ModSecurity 3.x through 3.0.5 mishandles excessively nested JSON objects.

LOW 39CWE-674Published 2021-12-07 · Updated 2024-08-04

Key facts

Attack vector: Network
Privileges required: None
User interaction: None
Attack complexity: Low
Impact type: Denial of service
Confidentiality · integrity · availability: None · None · High
Fix status: No fix listed

Attack profile from CVSS 3.1 · NVD. Fix status from CNA. Impact type from CWE-674.

Summary

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.

Why it matters now

EPSS 0.03249 88th percentileScored 2026-11-07

Public exploit Yes 1 exploit referenceTagged by NVD

Fix No fix listed No fixed version in the sources yet

SSVC decision points

Not available: CISA has not published SSVC decision points for this record.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
—	—	all versions	—	No fix listed	CNA

— Vendor— Affected all versions Fixed in — No fix listed CNA

CPE configurations NVD · 10

CPE	Versions	Role	Vendor
cpe:2.3:a:owasp:modsecurity::::::::	3.0.0 to before 3.0.6	Vulnerable	owasp-modsecurity
cpe:2.3:a:trustwave:modsecurity::::::::	2.0.0 to before 2.9.5	Vulnerable	Trustwave
cpe:2.3:a:f5:nginx_modsecurity_waf:r24:::::::*	r24	Vulnerable	F5
cpe:2.3:a:f5:nginx_modsecurity_waf:r25:::::::*	r25	Vulnerable	F5
cpe:2.3:o:debian:debian_linux:9.0:::::::*	9.0	Vulnerable	Debian
cpe:2.3:o:debian:debian_linux:10.0:::::::*	10.0	Vulnerable	Debian
cpe:2.3:o:debian:debian_linux:11.0:::::::*	11.0	Vulnerable	Debian
cpe:2.3:a:oracle:http_server:12.2.1.3.0:::::::*	12.2.1.3.0	Vulnerable	Oracle
cpe:2.3:a:oracle:http_server:12.2.1.4.0:::::::*	12.2.1.4.0	Vulnerable	Oracle
cpe:2.3:a:oracle:zfs_storage_appliance_kit:8.8:::::::*	8.8	Vulnerable	Oracle

cpe:2.3:a:owasp:modsecurity:*:*:*:*:*:*:*:* Versions 3.0.0 to before 3.0.6 Vulnerable ·owasp-modsecurity
cpe:2.3:a:trustwave:modsecurity:*:*:*:*:*:*:*:* Versions 2.0.0 to before 2.9.5 Vulnerable ·Trustwave
cpe:2.3:a:f5:nginx_modsecurity_waf:r24:*:*:*:*:*:*:* Versions r24 Vulnerable ·F5
cpe:2.3:a:f5:nginx_modsecurity_waf:r25:*:*:*:*:*:*:* Versions r25 Vulnerable ·F5
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:* Versions 9.0 Vulnerable ·Debian
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:* Versions 10.0 Vulnerable ·Debian
cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:* Versions 11.0 Vulnerable ·Debian
cpe:2.3:a:oracle:http_server:12.2.1.3.0:*:*:*:*:*:*:* Versions 12.2.1.3.0 Vulnerable ·Oracle
cpe:2.3:a:oracle:http_server:12.2.1.4.0:*:*:*:*:*:*:* Versions 12.2.1.4.0 Vulnerable ·Oracle
cpe:2.3:a:oracle:zfs_storage_appliance_kit:8.8:*:*:*:*:*:*:* Versions 8.8 Vulnerable ·Oracle

Remediation

No fixed version listed by the sources yet.

Vendor assessments

Red Hat

Red Hat's page for this CVE →

Not affected: 1 product

Red Hat

Timeline

2026-10-02 Threatist record created from CVE-2021-42717
2026-10-03 Alias added: GHSA-w3vf-7fpc-9fww

References

Exploit 1

https://www.trustwave.com/en-us/resources/blogs/spiderlabs-blog/modsecurity-dos-vulnerability-in-json-parsing-cve-2021-42717/

Patch 1

https://www.oracle.com/security-alerts/cpuapr2022.html

Advisory 2

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences