CVE-2021-42717

mediumpriority · track · 41EPSS 0.032 · 88 %ileexploit · PoCDEEURUUS

grimoire priorityP1 · Urgent

Exploitable?

Public exploit

1 exploit · PoC

Likely / severe?

3.25% (88th) EPSS

CVSS 5 · medium

Is it mine?

20 products

Check your exposure

Who says so?

6 sources

cnnvd · enisa_euvd · fstec_bdu · osv

EPSS · scored 2026-10-27

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.

cvss

Technical severity, 0–10. One row per scoring source.

7.5

010

base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · medium–high · 5–7.5

v2.05mediumAV:N/AC:L/Au:N/C:N/I:N/A:Pprimary · NVD / NIST USexploitability 10 · impact 2.9

v3.17.5highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Hprimary · NVD / NIST USexploitability 3.9 · impact 3.6

v3.17.5highAV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Hsecondary · FSTEC (BDU) RU

v3.17.1highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:Psecondary · CVSS-BT (t0sche)

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-674USprimaryCWE-674US

exploits (1)

Public proof-of-concept and weaponised exploit code.

EkamSinghWalia/Detection-and-Mitigation-script-for-CVE-2021-42717Detection and Mitigation script for CVE-2021-42717 -> ModSecurity DoS Vulnerability in JSON Parsing PoC · poc_in_github

affected products (20)

Products and version ranges known to be affected.

Oracle Linuxall versionscert_bundDEcpe:/o:oracle:linux:-
Xerox FreeFlow Print Server 7all versionscert_bundDEcpe:/a:xerox:freeflow_print_server:7
Xerox FreeFlow Print Server 9all versionscert_bundDEcpe:/a:xerox:freeflow_print_server:9
n/a n/a≤ n/aenisa_euvdEU
SpiderLabs ModSecurity2.0.0 → 2.9.5fstec_bduRU
SpiderLabs ModSecurity3.0.0 → 3.0.6fstec_bduRU
Сообщество свободного программного обеспечения Debian GNU/Linux≤ 10fstec_bduRU
Сообщество свободного программного обеспечения Debian GNU/Linux≤ 11fstec_bduRU
debian debian linux= 10.0nvdUScpe:2.3:o:debian:debian_linux:*:*:*:*:*:*:*:*
debian debian linux= 11.0nvdUScpe:2.3:o:debian:debian_linux:*:*:*:*:*:*:*:*
debian debian linux= 9.0nvdUScpe:2.3:o:debian:debian_linux:*:*:*:*:*:*:*:*
f5 nginx modsecurity waf= r24nvdUScpe:2.3:a:f5:nginx_modsecurity_waf:*:*:*:*:*:*:*:*
f5 nginx modsecurity waf= r25nvdUScpe:2.3:a:f5:nginx_modsecurity_waf:*:*:*:*:*:*:*:*
oracle http server= 12.2.1.3.0nvdUScpe:2.3:a:oracle:http_server:*:*:*:*:*:*:*:*
oracle http server= 12.2.1.4.0nvdUScpe:2.3:a:oracle:http_server:*:*:*:*:*:*:*:*
oracle zfs storage appliance kit= 8.8nvdUScpe:2.3:a:oracle:zfs_storage_appliance_kit:*:*:*:*:*:*:*:*
owasp modsecurity3.0.0 → 3.0.6nvdUScpe:2.3:a:owasp:modsecurity:*:*:*:*:*:*:*:*
trustwave modsecurity2.0.0 → 2.9.5nvdUScpe:2.3:a:trustwave:modsecurity:*:*:*:*:*:*:*:*
Bitnami modsecurity2.0.0 → 2.9.5osvUSpkg:bitnami/modsecurity
Bitnami modsecurity22.0.0 → 2.9.5osvUSpkg:bitnami/modsecurity2

advisories (6)

Vendor and ecosystem advisories describing this.

WID-SEC-W-2022-0302Xerox FreeFlow Print Server: Mehrere Schwachstellen ermöglichen Ausführen von beliebigem Programmcode mit AdministratorrechtenDeutsch2022-06-14csaf · cert_bundDE
Ein entfernter, authentisierter Angreifer kann mehrere Schwachstellen in Xerox FreeFlow Print Server ausnutzen, um beliebigen Programmcode auszuführen, einen Cross-Site-Scripting-Angriff durchzuführen, Informationen offenzulegen, einen Denial-of-Service-Zustand zu verursachen oder Dateien zu manipulieren.
WID-SEC-W-2022-0432Xerox FreeFlow Print Server: Mehrere SchwachstellenDeutsch2022-06-21csaf · cert_bundDE
Ein entfernter, authentisierter Angreifer kann mehrere Schwachstellen in Xerox FreeFlow Print Server ausnutzen, um die Vertraulichkeit, Verfügbarkeit und Integrität zu gefährden.
WID-SEC-W-2023-0132Oracle Fusion Middleware: Mehrere SchwachstellenDeutsch2023-01-17csaf · cert_bundDE
Ein entfernter, anonymer Angreifer kann mehrere Schwachstellen in Oracle Fusion Middleware ausnutzen, um die Vertraulichkeit, Integrität und Verfügbarkeit zu gefährden.
WID-SEC-W-2023-1578Trustwave ModSecurity: Schwachstelle ermöglicht Denial of ServiceDeutsch2021-12-07csaf · cert_bundDE
Ein entfernter, anonymer Angreifer kann eine Schwachstelle in Trustwave ModSecurity ausnutzen, um einen Denial of Service Angriff durchzuführen.
BIT-modsecurity-2021-427172024-03-06vendor · osvUS
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.
BIT-modsecurity2-2021-427172024-03-06vendor · osvUS
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.

also known as (6)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd fstec_bdu osv cert_bund nvd NVD CVE.org MITRE

published 2021-12-07modified 2026-06-17

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+719 more

references (17)

External citations — patches, advisories, analysis.

scry

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