CVE-2020-18780

Assembler crash via interior allocation pointer

Published Aug 22, 2023 · Updated Oct 4, 2024

Use after free in NASM 2.14.02 allows local users to crash the assembler through a crafted NASM command that another user runs. In expand_one_smacro in asm/preproc.c, mempcpy advances the allocation pointer, and the code passes that interior pointer to set_text_free instead of the allocation's start. Execution requires local access and user interaction; the documented consequence is a crash of the NASM command-line process, not broader system compromise.

CVSS severity5.5
Medium
EPSS probability0.29%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use after free in NASM 2.14.02 allows local users to crash the assembler through a crafted NASM command that another user runs. In expand_one_smacro in asm/preproc.c, mempcpy advances the allocation pointer, and the code passes that interior pointer to set_text_free instead of the allocation's start. Execution requires local access and user interaction; the documented consequence is a crash of the NASM command-line process, not broader system compromise.

The record

CVE
CVE-2020-18780
Published
Aug 22, 2023
Updated
Oct 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-416
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 22, 2023CVE publishedPublication date reported by the CVE source.
  2. Oct 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

5.5NIST National Vulnerability DatabaseCVSS: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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-416Use After Free

Public exploit references

No public exploit references are available in this record.

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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