Vulnerability in F5 nginx Modsecurity Waf
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 · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.032 (88.1th percentile), scored .
Low probability of exploitation in the next 30 days, but still tracked. 88th percentile — 88.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.031 · newest: 0.032 · change: +0.001
Affected products
- F5 nginx Modsecurity Waf — versions r24, r25
- Oracle HTTP Server — versions 12.2.1.3.0, 12.2.1.4.0
- Oracle Zfs Storage Appliance Kit — versions 8.8
- Owasp Modsecurity
- Trustwave Modsecurity
- Debian Linux — versions 9.0, 10.0, 11.0
Weakness classification (CWE)
Public proof-of-concept exploits
References
- www.debian.org/security/2021/dsa-5023 (vendor-advisory, Third Party Advisory)
- www.oracle.com/security-alerts/cpuapr2022.html (Patch, Third Party Advisory)
- www.trustwave.com/en-us/resources/blogs/spiderlabs-blog/modsecurity-dos-vulnera… (Exploit, Mitigation, Vendor Advisory)
- lists.debian.org/debian-lts-announce/2022/05/msg00042.html (mailing-list, Mailing List, Third Party Advisory)
Frequently asked questions
- What is CVE-2021-42717?
- CVE-2021-42717 is a high-severity vulnerability in F5 nginx Modsecurity Waf, classified under Uncontrolled Recursion. CVSS score: 7.5/10. Published 2021-12-07.
- How severe is CVE-2021-42717?
- High severity. CVSS v3 base score is 7.5 out of 10.
- Is CVE-2021-42717 known to be exploited?
- 2 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.