CVE-2023-31725Public exploit

Assembler crash via freed macro object read

Published May 17, 2023 · Updated Jan 22, 2025

Use-after-free in Yasm 1.3.0.55.g101bc allows context-dependent attackers to crash the assembler via a crafted source file. During NASM macro preprocessing, pp_getline frees a macro object through free_mmacro, but expand_mmac_params later reads eight bytes from that released heap allocation. The victim must run Yasm on the crafted file; the demonstrated outcome is process termination under AddressSanitizer, with no reported data exposure or code execution.

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 Yasm 1.3.0.55.g101bc allows context-dependent attackers to crash the assembler via a crafted source file. During NASM macro preprocessing, pp_getline frees a macro object through free_mmacro, but expand_mmac_params later reads eight bytes from that released heap allocation. The victim must run Yasm on the crafted file; the demonstrated outcome is process termination under AddressSanitizer, with no reported data exposure or code execution.

The record

CVE
CVE-2023-31725
Published
May 17, 2023
Updated
Jan 22, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-416, T1204.002
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 17, 2023CVE publishedPublication date reported by the CVE source.
  2. Jan 22, 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 privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

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

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-416Use After Free
T1204.002Malicious 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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