CVE-2021-3918· NVD / CVE Program· CNA @huntrdev

Prototype Pollution in kriszyp/json-schema

json-schema is vulnerable to Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

CriticalCVSS 9.8 · v3.1—No exploit Fix available

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Published: Nov 13, 2021
Updated: Jun 17, 2026
EPSS: 3.8% · 90th percentile
CWE: CWE-1321

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Action score

Plan

Add it to your regular patch cycle.

CVSS: 39 / 40 · 9.8 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 1 / 30 · 3.8%

CNA vs NVD score

NVD: 9.8
CNA · @huntrdev: 9.8; agree

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Affected systems

Vendor	Product	CPE
json-schema project	json-schema	cpe:2.3:a:json-schema_project:json-schema
debian	debian linux	cpe:2.3:o:debian:debian_linux

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

debian debian linux10.0
json-schema project json-schemabefore 0.4.0

Versions reported by the vendor

Affected version ranges reported by the assigning authority (@huntrdev). Independent of NVD's CPE analysis and usually ahead of it.

kriszyp kriszyp/json-schema
- unspecified and later · up to and including 0.3.0affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

+96

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
almalinux:nodejs	1:16.13.1-3.module_el8.5.0+2605+45d748af · AlmaLinux:8	Package registry (OSV)
almalinux:nodejs-devel	1:16.13.1-3.module_el8.5.0+2605+45d748af · AlmaLinux:8	Package registry (OSV)
almalinux:nodejs-docs	1:16.13.1-3.module_el8.5.0+2605+45d748af · AlmaLinux:8	Package registry (OSV)
almalinux:nodejs-full-i18n	1:16.13.1-3.module_el8.5.0+2605+45d748af · AlmaLinux:8	Package registry (OSV)
almalinux:nodejs-nodemon	2.0.15-1.module_el8.6.0+2904+f21ad6f4 · AlmaLinux:8	Package registry (OSV)
almalinux:nodejs-packaging	25-1.module_el8.5.0+246+05401605 · AlmaLinux:8	Package registry (OSV)
almalinux:npm	1:8.1.2-1.16.13.1.3.module_el8.5.0+2605+45d748af · AlmaLinux:8	Package registry (OSV)
debian:node-json-schema	0.4.0+~7.0.9-1 · Debian:12	Package registry (OSV)
npm:json-schema	0.4.0	Package registry (OSV)
opensuse:bind	9.16.6-150000.12.65.1 · openSUSE:Leap 15.4	Package registry (OSV)
opensuse:dracut-saltboot	0.1.1681904360.84ef141-150000.1.50.1 · openSUSE:Leap 15.4	Package registry (OSV)
opensuse:grafana	9.5.8-150200.3.53.2 · openSUSE:Leap 15.5	Package registry (OSV)
opensuse:nodejs10	10.24.1-150000.1.44.1 · openSUSE:Leap 15.3	Package registry (OSV)
red hat:nodejs	1:12.22.12-1.module+el8.1.0+15296+87b2f6ad · Red Hat:rhel_e4s:8.1::appstream	Package registry (OSV)
red hat:nodejs-debuginfo	1:12.22.12-1.module+el8.1.0+15296+87b2f6ad · Red Hat:rhel_e4s:8.1::appstream	Package registry (OSV)
red hat:nodejs-debugsource	1:12.22.12-1.module+el8.1.0+15296+87b2f6ad · Red Hat:rhel_e4s:8.1::appstream	Package registry (OSV)
red hat:nodejs-devel	1:12.22.12-1.module+el8.1.0+15296+87b2f6ad · Red Hat:rhel_e4s:8.1::appstream	Package registry (OSV)
red hat:nodejs-docs	1:12.22.12-1.module+el8.1.0+15296+87b2f6ad · Red Hat:rhel_e4s:8.1::appstream	Package registry (OSV)
red hat:nodejs-full-i18n	1:12.22.12-1.module+el8.1.0+15296+87b2f6ad · Red Hat:rhel_e4s:8.1::appstream	Package registry (OSV)
red hat:nodejs-nodemon	0:1.18.3-1.module+el8.1.0+3369+37ae6a45 · Red Hat:rhel_e4s:8.1::appstream	Package registry (OSV)
red hat:nodejs-packaging	0:17-3.module+el8.1.0+3369+37ae6a45 · Red Hat:rhel_e4s:8.1::appstream	Package registry (OSV)
red hat:npm	1:6.14.16-1.12.22.12.1.module+el8.1.0+15296+87b2f6ad · Red Hat:rhel_e4s:8.1::appstream	Package registry (OSV)
red hat:rh-nodejs14-nodejs	0:14.18.2-1.el7 · Red Hat:rhel_software_collections:3::el7	Package registry (OSV)
red hat:rh-nodejs14-nodejs-debuginfo	0:14.18.2-1.el7 · Red Hat:rhel_software_collections:3::el7	Package registry (OSV)
red hat:rh-nodejs14-nodejs-devel	0:14.18.2-1.el7 · Red Hat:rhel_software_collections:3::el7	Package registry (OSV)
rocky linux:nodejs	1:16.13.1-3.module+el8.5.0+721+4c107270 · Rocky Linux:8	Package registry (OSV)
rocky linux:nodejs-nodemon	0:2.0.15-1.module+el8.5.0+721+4c107270 · Rocky Linux:8	Package registry (OSV)
rocky linux:nodejs-packaging	0:25-1.module+el8.6.0+1046+80feca58 · Rocky Linux:8	Package registry (OSV)
suse:bind	9.16.6-150000.12.65.1 · SUSE:Manager Client Tools for SLE Micro 5	Package registry (OSV)
suse:dracut-saltboot	0.1.1681904360.84ef141-150000.1.50.1 · SUSE:Manager Client Tools 15	Package registry (OSV)

+11

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

kriszyp/json-schemacommit 22f1461

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

Anyone who can reach it over the internet can trigger it.
No account or password is required.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality: high · data can be read
Integrity: high · data or configuration can be modified
Availability: high · the service can be disrupted

Attack vector: Network
Attack complexity: Low
Privileges required: None
User interaction: None
Scope: Unchanged
Confidentiality impact: High
Integrity impact: High
Availability impact: High

Weakness class (CWE)

CWE-1321 · Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Attack patterns (CAPEC)

ATT&CK techniques

Hijack Execution Flow: ServicesFile Permissions WeaknessT1574.010

Change log

Fix✗ → ✓Sep 28, 2026, 10:45 PM UTC

For records you follow, these changes also arrive as notifications. →

References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records

Noroxi analysis

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Data sources and verification

CNA: @huntrdev

CVE.org (CNA)Jan 17, 2025, 8:02 PM UTC
NVDJun 17, 2026, 12:05 AM UTC
FIRST EPSSSep 29, 2026, 12:00 AM UTC
OSV / GHSASep 30, 2026, 3:23 AM UTC

Each line is when that source was last processed for this record.

You’re seeing every CVE. Add your stack to narrow the list down to the ones that affect you.

Add your stack

Ecosystem	Package	Affected range	Fix
AlmaLinux:8	nodejs	before 1:16.13.1-3.module_el8.5.0+246+05401605	1:16.13.1-3.module_el8.5.0+246+05401605
AlmaLinux:8	nodejs	before 1:14.18.2-2.module_el8.5.0+2618+8d46dafd	1:14.18.2-2.module_el8.5.0+2618+8d46dafd
AlmaLinux:8	nodejs	before 1:14.18.2-2.module_el8.5.0+254+b4526b16	1:14.18.2-2.module_el8.5.0+254+b4526b16
AlmaLinux:8	nodejs	before 1:16.13.1-3.module_el8.5.0+2605+45d748af	1:16.13.1-3.module_el8.5.0+2605+45d748af
AlmaLinux:8	nodejs-devel	before 1:16.13.1-3.module_el8.5.0+2605+45d748af	1:16.13.1-3.module_el8.5.0+2605+45d748af
AlmaLinux:8	nodejs-devel	before 1:14.18.2-2.module_el8.5.0+2618+8d46dafd	1:14.18.2-2.module_el8.5.0+2618+8d46dafd
AlmaLinux:8	nodejs-devel	before 1:14.18.2-2.module_el8.5.0+254+b4526b16	1:14.18.2-2.module_el8.5.0+254+b4526b16
AlmaLinux:8	nodejs-devel	before 1:16.13.1-3.module_el8.5.0+246+05401605	1:16.13.1-3.module_el8.5.0+246+05401605
AlmaLinux:8	nodejs-docs	before 1:14.18.2-2.module_el8.5.0+254+b4526b16	1:14.18.2-2.module_el8.5.0+254+b4526b16
AlmaLinux:8	nodejs-docs	before 1:14.18.2-2.module_el8.5.0+2618+8d46dafd	1:14.18.2-2.module_el8.5.0+2618+8d46dafd
AlmaLinux:8	nodejs-docs	before 1:16.13.1-3.module_el8.5.0+2605+45d748af	1:16.13.1-3.module_el8.5.0+2605+45d748af
AlmaLinux:8	nodejs-docs	before 1:16.13.1-3.module_el8.5.0+246+05401605	1:16.13.1-3.module_el8.5.0+246+05401605
AlmaLinux:8	nodejs-full-i18n	before 1:16.13.1-3.module_el8.5.0+246+05401605	1:16.13.1-3.module_el8.5.0+246+05401605
AlmaLinux:8	nodejs-full-i18n	before 1:14.18.2-2.module_el8.5.0+254+b4526b16	1:14.18.2-2.module_el8.5.0+254+b4526b16
AlmaLinux:8	nodejs-full-i18n	before 1:14.18.2-2.module_el8.5.0+2618+8d46dafd	1:14.18.2-2.module_el8.5.0+2618+8d46dafd
AlmaLinux:8	nodejs-full-i18n	before 1:16.13.1-3.module_el8.5.0+2605+45d748af	1:16.13.1-3.module_el8.5.0+2605+45d748af
AlmaLinux:8	nodejs-nodemon	before 2.0.15-1.module_el8.6.0+2904+f21ad6f4	2.0.15-1.module_el8.6.0+2904+f21ad6f4
AlmaLinux:8	nodejs-nodemon	before 2.0.15-1.module_el8.5.0+2605+45d748af	2.0.15-1.module_el8.5.0+2605+45d748af
AlmaLinux:8	nodejs-nodemon	before 2.0.15-1.module_el8.5.0+2618+8d46dafd	2.0.15-1.module_el8.5.0+2618+8d46dafd
AlmaLinux:8	nodejs-packaging	before 23-3.module_el8.5.0+2618+8d46dafd	23-3.module_el8.5.0+2618+8d46dafd
AlmaLinux:8	nodejs-packaging	before 23-3.module_el8.4.0+2522+3bd42762	23-3.module_el8.4.0+2522+3bd42762
AlmaLinux:8	nodejs-packaging	before 25-1.module_el8.5.0+2605+45d748af	25-1.module_el8.5.0+2605+45d748af
AlmaLinux:8	nodejs-packaging	before 25-1.module_el8.5.0+246+05401605	25-1.module_el8.5.0+246+05401605
AlmaLinux:8	npm	before 1:6.14.15-1.14.18.2.2.module_el8.5.0+2618+8d46dafd	1:6.14.15-1.14.18.2.2.module_el8.5.0+2618+8d46dafd