CVE-2021-45257
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 · uneditedAn infinite loop vulnerability exists in nasm 2.16rc0 via the gpaste_tokens function.
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 confidenceAn infinite loop vulnerability exists in nasm 2.16rc0 within the gpaste_tokens function. This type of flaw causes the program to enter an endless iteration cycle without proper exit conditions, leading to denial of service by consuming CPU resources indefinitely until the process is terminated.
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= 2.16CVSS 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 checksWork through these to decide whether this CVE applies to you.
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Verify nasm is installedRun `nasm -v` or `which nasm` to confirm the nasm binary exists on the systemAffected if nasm is not installed on the system - this CVE does not apply
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Determine installed nasm versionExecute `nasm -v` and note the version string returnedAffected if the version displayed is anything other than 2.16rc0 - only exactly version 2.16rc0 is affected
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Check for presence of gpaste_tokens function usageReview any custom macros, preprocessor directives, or assembly code that may invoke the gpaste_tokens function during assembly. This function is part of the nasm preprocessor macro expansion logic.Affected if the gpaste_tokens function is invoked during assembly operations - the infinite loop triggers when this function processes certain macro expansions
The user is affected only if nasm version 2.16rc0 is installed AND the gpaste_tokens function is exercised during the assembly process, causing an infinite loop that hangs the process.
Generated from the published advisory. Verify against your own configuration.
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 · scopedUpdate nasm to a patched version beyond 2.16rc0, or review and fix the loop termination logic in the gpaste_tokens function to ensure proper exit conditions exist.
nasm 2.16 stable or later (2.16.01, 2.16.1, or 2.17)
- 1. Identify the current nasm version by running: nasm --version
- 2. Download the latest stable nasm release from the official GitHub repository (https://github.com/netwide-assembler/nasm) or your distribution's package manager
- 3. If using a package manager, update to the latest available version: apt-get update && apt-get install nasm (Debian/Ubuntu) or yum/dnf update nasm (RHEL/CentOS/Fedora)
- 4. Verify the installation: nasm --version
- 5. Test your assembly workflows to confirm the toolchain functions correctly with the updated version
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,800.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-45257 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-45257 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- 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
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