CVE-2021-46524Public exploit

Heap over-read via JSON string quoting

Published Jan 27, 2022 · Updated Aug 4, 2024

Heap buffer overflow in Cesanta mJS 2.20.0 allows local users to crash an application by executing a crafted JavaScript file. The snquote routine iterates to a computed string boundary while quoting nested JSON, and the published test records a one-byte read immediately beyond a 214-byte heap allocation. Execution of attacker-supplied JavaScript is required; the demonstrated result is an AddressSanitizer abort, while code execution has not been shown.

CVSS severity7.8
High
EPSS probability0.74%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap buffer overflow in Cesanta mJS 2.20.0 allows local users to crash an application by executing a crafted JavaScript file. The snquote routine iterates to a computed string boundary while quoting nested JSON, and the published test records a one-byte read immediately beyond a 214-byte heap allocation. Execution of attacker-supplied JavaScript is required; the demonstrated result is an AddressSanitizer abort, while code execution has not been shown.

The record

CVE
CVE-2021-46524
Published
Jan 27, 2022
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-787, T1204.002
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 27, 2022CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
6.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:P

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1204.002User Execution: Malicious File

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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