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.
Exploits (1)
nomisec
SCANNER
by EkamSinghWalia · poc
https://github.com/EkamSinghWalia/Detection-and-Mitigation-script-for-CVE-2021-42717
References (4)
Scores
CVSS v3
7.5
EPSS
0.0204
EPSS Percentile
83.9%
Attack Vector
NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Details
CWE
CWE-674
Status
published
Products (10)
debian/debian_linux
9.0
debian/debian_linux
10.0
debian/debian_linux
11.0
f5/nginx_modsecurity_waf
r24
f5/nginx_modsecurity_waf
r25
oracle/http_server
12.2.1.3.0
oracle/http_server
12.2.1.4.0
oracle/zfs_storage_appliance_kit
8.8
owasp/modsecurity
3.0.0 - 3.0.6
trustwave/modsecurity
2.0.0 - 2.9.5
Published
Dec 07, 2021
Tracked Since
Feb 18, 2026