CVE-2020-21528

Assembler crash via null IEEE segment name

Published Aug 22, 2023 · Updated Aug 4, 2024

Null-pointer dereference in NASM 2.14.03 and 2.15 allows attackers to crash the assembler by processing a crafted assembly file. The ieee_segment function in output/outieee.c can leave seg->name null after label handling and dereference the unset pointer while defining later IEEE 695 segments. Execution requires a user or build process to invoke NASM on attacker-supplied IEEE-output input, and the resulting segmentation fault terminates that NASM process.

CVSS severity5.5
Medium
EPSS probability0.54%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Null-pointer dereference in NASM 2.14.03 and 2.15 allows attackers to crash the assembler by processing a crafted assembly file. The ieee_segment function in output/outieee.c can leave seg->name null after label handling and dereference the unset pointer while defining later IEEE 695 segments. Execution requires a user or build process to invoke NASM on attacker-supplied IEEE-output input, and the resulting segmentation fault terminates that NASM process.

The record

CVE
CVE-2020-21528
Published
Aug 22, 2023
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1204.002
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 22, 2023CVE 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

5.5NIST 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.

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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 exploitUnconfirmed

Weakness, pattern, technique

T1204.002Malicious File

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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