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.

• CWE-674

• https://lists.debian.org/debian-lts-announce/2022/05/msg00042.htmlMailing List, Third Party Advisory
• https://www.debian.org/security/2021/dsa-5023Third Party Advisory
• https://www.oracle.com/security-alerts/cpuapr2022.htmlPatch, Third Party Advisory
• https://www.trustwave.com/en-us/resources/blogs/spiderlabs-blog/modsecurity-dos-vulnerability-in-json-parsing-cve-2021-42717/Exploit, Mitigation, Vendor Advisory
• https://lists.debian.org/debian-lts-announce/2022/05/msg00042.htmlMailing List, Third Party Advisory
• https://www.debian.org/security/2021/dsa-5023Third Party Advisory
• https://www.oracle.com/security-alerts/cpuapr2022.htmlPatch, Third Party Advisory
• https://www.trustwave.com/en-us/resources/blogs/spiderlabs-blog/modsecurity-dos-vulnerability-in-json-parsing-cve-2021-42717/Exploit, Mitigation, Vendor Advisory

Published

Dec 7, 2021

Last Modified

Jun 17, 2026

Status

Modified

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