CVE-2021-36535Public exploit

Interpreter crash via error-reporting heap over-read

Published Feb 3, 2023 · Updated Mar 26, 2025

Heap buffer overflow in Cesanta mJS 1.26 allows local users to crash the interpreter by executing a crafted JavaScript file. While parse_literal reports an error, mjs_set_errorf dereferences a wild pointer and reads eight bytes beyond the heap buffer. Triggering the fault requires low-privilege local execution of the interpreter; the demonstrated consequence is process abort, with no reported data disclosure or modification.

CVSS severity5.5
Medium
EPSS probability0.37%
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 1.26 allows local users to crash the interpreter by executing a crafted JavaScript file. While parse_literal reports an error, mjs_set_errorf dereferences a wild pointer and reads eight bytes beyond the heap buffer. Triggering the fault requires low-privilege local execution of the interpreter; the demonstrated consequence is process abort, with no reported data disclosure or modification.

The record

CVE
CVE-2021-36535
Published
Feb 3, 2023
Updated
Mar 26, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-787, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 3, 2023CVE publishedPublication date reported by the CVE source.
  2. Mar 26, 2025Record 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 privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.5NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
5.5CISA-ADPCVSS:3.1/AV:L/AC:L/PR:L/UI:N/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.

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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1499.004Application or System Exploitation

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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