CVE-2021-42717
HIGH
Published Dec 7, 20214y ago · Modified Jun 17, 20262w ago
7.5 CVSS 3.1
Published Dec 7, 2021 4y ago
Last Modified Jun 17, 2026 2w ago
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.
CVSS Details
Base Score
Exploitability
Impact
Vector string
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Attack Vector Network
Attack Complexity Low
Privileges Required None
User Interaction None
Scope Unchanged
Confidentiality None
Integrity None
Availability High
Threat Intelligence
No active exploitation signals — not in CISA KEV and no EPSS score yet.
Exploit & Patch Status
Public Exploit Known
Patch Available
Weaknesses 1
CWE-674
Affected Products 10
| Vendor | Product | Version | Range |
|---|---|---|---|
| owasp | modsecurity | * | ≥3.0.0 – <3.0.6 |
| trustwave | modsecurity | * | ≥2.0.0 – <2.9.5 |
| f5 | nginx_modsecurity_waf | r24 | any |
| f5 | nginx_modsecurity_waf | r25 | any |
| debian | debian_linux | 9.0 | any |
| debian | debian_linux | 10.0 | any |
| debian | debian_linux | 11.0 | any |
| oracle | http_server | 12.2.1.3.0 | any |
| oracle | http_server | 12.2.1.4.0 | any |
| oracle | zfs_storage_appliance_kit | 8.8 | any |
References 4
- lists.debian.org https://lists.debian.org/debian-lts-announce/2022/05/msg00042.html
- debian.org https://www.debian.org/security/2021/dsa-5023
- oracle.com https://www.oracle.com/security-alerts/cpuapr2022.html
- trustwave.com https://www.trustwave.com/en-us/resources/blogs/spiderlabs-blog/modsecurity-dos-vulnerability-in-json-parsing-cve-2021-42717/
Remediation
- oracle.com https://www.oracle.com/security-alerts/cpuapr2022.html