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CVE-2021-4279

31
FAUCET Score

CVE-2021-4279 is a critical prototype pollution vulnerability affecting Starcounter-Jack JSON-Patch up to version 3.1.0. This flaw allows for improperly controlled modification of object prototype attributes, impacting the integrity and availability of applications utilizing the affected library. With a CVSS score of 9.8 (Critical), it is easily exploitable remotely with low attack complexity, potentially leading to complete compromise of confidentiality, integrity, and availability. While the exploit has been publicly disclosed, there is currently no evidence of active exploitation, Metasploit modules, or significant community discussion or media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
< 3.1.1CPE matchmatch criteria
cpe:2.3:a:starcounter-jack:json-patch:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

6.3MEDIUM

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
LOW
Integrity Impact
LOW
Availability Impact
LOW
Exploitability Score
2.8
Impact Score
3.4
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.08%
Probability of exploitation in next 30 days
EPSS Percentile
61.7%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0108 is in the 47th percentile among its peer group of 36,835 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (2)

github_advisorypatch availablevia nvd_reference
View patch
npmpatch availablevia ghsa
Product: fast-json-patchFixed in: 3.1.1

Vendor Advisories (1)

npmGHSA-8gh8-hqwg-xf34high

Starcounter-Jack JSON-Patch Prototype Pollution vulnerability

Dec 25, 2022

References

github.com / Starcounter-Jack/JSON-Patch/commit/7ad6af41eabb2d799f698740a91284d762c955c9
PatchThird Party Advisory
github.com / Starcounter-Jack/JSON-Patch/pull/262
ExploitPatchThird Party Advisory
github.com / Starcounter-Jack/JSON-Patch/releases/tag/3.1.1
Release NotesThird Party Advisory
vuldb.com
Third Party Advisory
vuldb.com
Third Party Advisory