Security readout for executives and security teams
Plain-English summary
NASM, an assembler used in software build workflows, can crash when processing a specially crafted assembly file. The documented impact is denial of service, not code execution. Business urgency depends on whether your build, analysis, or packaging systems process untrusted assembly source.
Executive priority
Treat this as a targeted build-tool denial-of-service risk. It is not currently supported as actively exploited or code-execution capable in the provided sources, but exposed automated build systems should be remediated promptly.
Technical view
CVE-2020-21528 is a segmentation fault in NASM's ieee_segment function in outieee.c. The CVE description names NASM 2.14.03 and 2.15 and says crafted assembly input can trigger denial of service. Public metadata does not provide CVSS, CWE, or complete affected-product records.
Likely exposure
Exposure is most likely in developer workstations, CI systems, package builders, or automated analysis pipelines using NASM 2.14.03 or 2.15 on untrusted assembly files.
Exploitation context
The source bundle does not show CISA KEV listing or cited evidence of active exploitation. The described attack condition is processing a crafted assembly file that causes NASM to crash.
Researcher notes
The CVE record contains limited metadata: severity is unknown, CVSS is absent, and affected entries are listed as n/a despite the description naming NASM versions. Validate exact fixed versions from vendor advisories before asserting patch status.
Mitigation direction
- Inventory NASM installations and versions across developer, CI, and build environments.
- Check NASM and distribution vendor guidance, including Gentoo GLSA-202312-09, for fixed package versions.
- Prioritize updating systems that process external or user-submitted assembly files.
- Restrict untrusted assembly input to isolated build or analysis environments.
- Monitor build failures for repeated NASM crashes tied to external source inputs.
Validation and detection
- Confirm whether NASM 2.14.03 or 2.15 is present in package inventories or SBOMs.
- Review CI and packaging jobs for workflows that assemble untrusted or third-party source.
- Verify remediation status against vendor advisories before closing the finding.
- Check logs for recurring assembler segmentation faults during untrusted source processing.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CVE-2020-21528 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Unknown
- CVSS
- Not scored
- Known Exploited
- No
- Published
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS and timeline data
No CVSS vectors or timeline events were available in the normalized CVE source material.
Source materials
- CVE List V5 sourceCVE List V5
- https://bugzilla.nasm.us/show_bug.cgi?id=3392637CVE reference
- GLSA-202312-09CVE reference · vendor-advisory
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.