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Fencer Intel
high 7.2

CVE-2020-7777 json

Arbitrary Code Execution

published 5y ago modified 4mo ago also GHSA-vm64-cfqx-3698 , EUVD-2022-1210

cvss
7.2
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
2.1%
EPSS 2.1% chance of exploitation in 30 days, percentile 81%
public exploits
0
none known

Summary

This affects all versions of package jsen. If an attacker can control the schema file, it could run arbitrary JavaScript code on the victim machine. In the module description and README file there is no mention about the risks of untrusted schema files, so I assume that this is applicable. In particular the required field of the schema is not properly sanitized. The resulting string that is build based on the schema definition is then passed to a Function.apply();, leading to an Arbitrary Code Execution.

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Exploit prediction

2.11% chance of exploitation in the next 30 days, higher than 81% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • snyk.io https://snyk.io/vuln/SNYK-JS-JSEN-1014670 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 7.2 CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H/E:P/RL:U/RC:C
CNA 3.1 7.2 CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 6.5 AV:N/AC:L/Au:S/C:P/I:P/A:P
GitHub 3.1 7.2 CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

Affected packages

ecosystem package affected fixed in
npm jsen
<=0.6.6
 no fix listed

Affected products

  • n/a jsen

Classification

Weakness
  • CWE-94 Improper Control of Generation of Code

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.