Vulnerability Monitor

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CVE-2021-42717

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.

Published

2021-12-07T22:15:06.950

Last Modified

2025-07-03T20:59:18.650

Status

Modified

Source

[email protected]

Severity

CVSSv3.1: 7.5 (HIGH)

CVSSv2 Vector

AV:N/AC:L/Au:N/C:N/I:N/A:P

Access Vector: NETWORK
Access Complexity: LOW
Authentication: NONE
Confidentiality Impact: NONE
Integrity Impact: NONE
Availability Impact: PARTIAL

Exploitability Score

10.0

Impact Score

2.9

Weaknesses

Type: Primary
CWE-674

Affected Vendors & Products

Type	Vendor	Product	Version/Range	Vulnerable?
Application	owasp	modsecurity	< 3.0.6	Yes
Application	trustwave	modsecurity	< 2.9.5	Yes
Application	f5	nginx_modsecurity_waf	r24	Yes
Application	f5	nginx_modsecurity_waf	r25	Yes
Operating System	debian	debian_linux	9.0	Yes
Operating System	debian	debian_linux	10.0	Yes
Operating System	debian	debian_linux	11.0	Yes
Application	oracle	http_server	12.2.1.3.0	Yes
Application	oracle	http_server	12.2.1.4.0	Yes
Application	oracle	zfs_storage_appliance_kit	8.8	Yes

References

https://lists.debian.org/debian-lts-announce/2022/05/msg00042.html Mailing List, Third Party Advisory ([email protected])
https://www.debian.org/security/2021/dsa-5023 Third Party Advisory ([email protected])
https://www.oracle.com/security-alerts/cpuapr2022.html Patch, Third Party Advisory ([email protected])
https://www.trustwave.com/en-us/resources/blogs/spiderlabs-blog/modsecurity-dos-vulnerability-in-json-parsing-cve-2021-42717/ Exploit, Mitigation, Vendor Advisory ([email protected])
https://lists.debian.org/debian-lts-announce/2022/05/msg00042.html Mailing List, Third Party Advisory (af854a3a-2127-422b-91ae-364da2661108)
https://www.debian.org/security/2021/dsa-5023 Third Party Advisory (af854a3a-2127-422b-91ae-364da2661108)
https://www.oracle.com/security-alerts/cpuapr2022.html Patch, Third Party Advisory (af854a3a-2127-422b-91ae-364da2661108)
https://www.trustwave.com/en-us/resources/blogs/spiderlabs-blog/modsecurity-dos-vulnerability-in-json-parsing-cve-2021-42717/ Exploit, Mitigation, Vendor Advisory (af854a3a-2127-422b-91ae-364da2661108)