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Fencer Intel
medium 6.5

CVE-2020-7770 json

Prototype Pollution

published 5y ago modified 4mo ago also GHSA-7h43-gx24-p529 , EUVD-2021-0999

cvss
6.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.9%
EPSS 1.9% chance of exploitation in 30 days, percentile 79%
public exploits
0
none known

Summary

This affects the package json8 before 1.0.3. The function adds in the target object the property specified in the path, however it does not properly check the key being set, leading to a prototype pollution.

Patch / fix

  • npm json8 1.0.3
  • n/a json8 1.0.3

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Exploit prediction

1.89% chance of exploitation in the next 30 days, higher than 79% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • snyk.io https://snyk.io/vuln/SNYK-JS-JSON8-1017116 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.5 AV:N/AC:L/Au:N/C:P/I:P/A:P
GitHub 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected packages

ecosystem package affected fixed in
npm json8
<1.0.3
1.0.3

Affected products

  • n/a json8

Classification

Weakness
  • CWE-1321 Improperly Controlled Modification of Object Prototype Attributes

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.