CVE-2021-46511Public exploit

Interpreter crash via mjs_pop_val assertion

Published Jan 27, 2022 · Updated Aug 4, 2024

Reachable assertion in Cesanta MJS 2.20.0 allows context-dependent attackers to crash the interpreter through crafted JavaScript. The mjs_pop_val function in src/mjs_core.c asserts that its internal buffer contains a full value and aborts when crafted execution leaves it shorter. The supplied proof of concept requires local execution or user interaction, and successful exploitation terminates only the affected MJS 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

Reachable assertion in Cesanta MJS 2.20.0 allows context-dependent attackers to crash the interpreter through crafted JavaScript. The mjs_pop_val function in src/mjs_core.c asserts that its internal buffer contains a full value and aborts when crafted execution leaves it shorter. The supplied proof of concept requires local execution or user interaction, and successful exploitation terminates only the affected MJS process.

The record

CVE
CVE-2021-46511
Published
Jan 27, 2022
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-617, 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

5.5NVDCVSS: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

CWE-617Reachable Assertion
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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