THREATPORT/VULNERABILITY/CVE-2021-42717
HIGH SEVERITY

CVE-2021-42717

Modsecurity vulnerability

CVSS
7.5
EPSS
3.2%
EPSS pct
87th
Exploited
No known
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.
Affected vendor
Owasp
Affected product
Modsecurity
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness type (CWE)
Published
2021-12-07

Risk analysis

Based on its CVSS vector, this vulnerability is exploitable over the network, low attack complexity, requiring no privileges, no user interaction. Successful exploitation leads to high impact to availability.

Its EPSS score of 3.2% reflects a lower probability of exploitation activity in the wild over the next 30 days, placing it above 87% of all scored CVEs.

Check your external exposure to CVE-2021-42717

  • Confirm whether Owasp Modsecurity is running on any internet-facing host or subdomain.
  • Match discovered service fingerprints against the version affected by CVE-2021-42717.
  • Prioritise remediation if the asset is public, business-critical, or near authentication/payment flows.

How ThreatPort helps with CVE-2021-42717

ThreatPort's external attack surface scanner checks your internet-facing assets — agentlessly, from the outside in — for the exposed services and versions that CVE-2021-42717 affects, then prioritises the finding by real risk using CISA KEV and FIRST.org EPSS.

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