CVE-2021-46531Public exploit

Interpreter crash via malformed decrement expression

Published Jan 27, 2022 · Updated Aug 4, 2024

Segmentation fault in Cesanta MJS 2.20.0 allows context-dependent attackers to crash the interpreter via crafted JavaScript. The published test case evaluates a malformed decrement expression involving JSON.parse and triggers an invalid write at mjs+0x8d28e, but no source function is identified. Execution of attacker-supplied JavaScript is required, and the demonstrated consequence is limited to aborting the interpreter process.

CVSS severity5.5
Medium
EPSS probability0.61%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Segmentation fault in Cesanta MJS 2.20.0 allows context-dependent attackers to crash the interpreter via crafted JavaScript. The published test case evaluates a malformed decrement expression involving JSON.parse and triggers an invalid write at mjs+0x8d28e, but no source function is identified. Execution of attacker-supplied JavaScript is required, and the demonstrated consequence is limited to aborting the interpreter process.

The record

CVE
CVE-2021-46531
Published
Jan 27, 2022
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1499
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

4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:N/A:P
5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

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.

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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

T1499Endpoint Denial of Service

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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