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Netwide AssemblerApplication · Nasm

CVE-2021-45256

MEDIUM · 5.5 CVSS v3.1 Published 2021-12-22
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
58/100
Remediation priority · Elevated
No privileges

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
A Null Pointer Dereference vulnerability existfs in nasm 2.16rc0 via asm/preproc.c.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

A Null Pointer Dereference vulnerability in nasm 2.16rc0 within asm/preproc.c can cause a denial of service (crash) when processing specially crafted assembly files through the preprocessor.

MitigationUpdate to a patched version of nasm when available, or avoid processing untrusted assembly source files with the affected version.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Netwide AssemblerApplication
Affected:= 2.16

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
None
User interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check installed nasm version
    Run `nasm --version` or `nasm -v` to retrieve the installed nasm version number
    Affected if The version displayed is 2.16 (including 2.16rc0)
  2. Verify preprocessor is in use
    Confirm you use nasm to assemble .asm or .s files that go through the preprocessor phase (this is the default behavior)
    Affected if You process assembly source files through nasm and the version is 2.16
  3. Identify if untrusted asm files are processed
    Review any automation, build scripts, or pipelines that invoke nasm on assembly files from external or untrusted sources
    Affected if Your nasm pipeline processes assembly files you did not author or that come from external sources and the version is 2.16

You are affected if nasm version 2.16 is installed and you process assembly files through its preprocessor, especially untrusted ones.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Update to a patched version of nasm when available, or avoid processing untrusted assembly source files with the affected version.

Recommended fix Moderate confidence

nasm 2.16.01 or latest stable release

  1. 1. Download the latest stable Netwide Assembler (nasm) release from the official repository at https://www.nasm.us/
  2. 2. Verify the GPG signature or checksum of the downloaded binary before installation
  3. 3. Replace the existing nasm installation with the new version
  4. 4. Verify the installation by running 'nasm --version'

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Netwide Assembler Scoped from the published advisory
  • Consultation1.0 h
  • Implementation2.0 h
  • Testing3.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,190
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Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-45256 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data