CVE-2023-31973Public exploit

Assembler crash via freed macro access

Published May 9, 2023 · Updated Aug 2, 2024

Use-after-free in Yasm 1.3.0 allows local users to crash the assembler by processing a crafted NASM-syntax source file. During preprocessing, pp_getline frees a macro object before expand_mmac_params reads a pointer inside that freed allocation. Exploitation requires processing untrusted source, and the upstream security policy disputes that this behavior has a security consequence.

CVSS severity5.5
Medium
EPSS probability0.31%
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 allows local users to crash the assembler by processing a crafted NASM-syntax source file. During preprocessing, pp_getline frees a macro object before expand_mmac_params reads a pointer inside that freed allocation. Exploitation requires processing untrusted source, and the upstream security policy disputes that this behavior has a security consequence.

The record

CVE
CVE-2023-31973
Published
May 9, 2023
Updated
Aug 2, 2024
Vendor
Tortall Networks
Product
Yasm
Classifications
CWE-401, CWE-590, T1204.002
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 9, 2023CVE publishedPublication date reported by the CVE source.
  2. Aug 2, 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1.3.0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Tortall Networks · Yasmversion=1.3.0

Published CVSS scores

7.8CISA-ADPCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
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-401Missing Release of Memory after Effective Lifetime
CWE-590Free of Memory not on the Heap
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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