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CVE-2021-42717

26
FAUCET Score

CVE-2021-42717 describes a denial-of-service vulnerability in ModSecurity versions 3.x through 3.0.5 and 2.8.0 through 2.9.4, affecting products like Debian, F5, Oracle, OWASP, and Trustwave. Attackers can craft excessively nested JSON objects to consume significant CPU resources and render the web server unable to process legitimate requests. With a CVSS score of 7.5 (High), this vulnerability is easily exploitable over the network with low attack complexity, leading to high availability impact. Currently, there is no evidence of active exploitation, public exploit code, or significant community discussion surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
>= 3.0.0, < 3.0.6CPE matchmatch criteria
cpe:2.3:a:owasp:modsecurity:*:*:*:*:*:*:*:*
>= 2.0.0, < 2.9.5CPE matchmatch criteria
cpe:2.3:a:trustwave:modsecurity:*:*:*:*:*:*:*:*
r24CPE matchmatch criteria
cpe:2.3:a:f5:nginx_modsecurity_waf:r24:*:*:*:*:*:*:*
r25CPE matchmatch criteria
cpe:2.3:a:f5:nginx_modsecurity_waf:r25:*:*:*:*:*:*:*
9.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

7.5HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
3.21%
Probability of exploitation in next 30 days
EPSS Percentile
86.8%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0321 is in the 76th percentile among its peer group of 51,506 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (1)

oraclepatch availablevia nvd_reference
View patch

References

lists.debian.org / debian-lts-announce/2022/05/msg00042.html
Mailing ListThird Party Advisory
debian.org / security/2021/dsa-5023
Third Party Advisory
oracle.com / security-alerts/cpuapr2022.html
PatchThird Party Advisory
trustwave.com / en-us/resources/blogs/spiderlabs-blog/modsecurity-dos-vulnerability-in-json-parsing-cve-2021-42717
ExploitMitigationVendor Advisory