NixApplication · Nix Project
CVE-2021-45707
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 issue was discovered in the nix crate 0.16.0 and later before 0.20.2, 0.21.x before 0.21.2, and 0.22.x before 0.22.2 for Rust. unistd::getgrouplist has an out-of-bounds write if a user is in more than 16 /etc/groups groups.
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 · high confidenceThe nix crate for Rust contains a heap-based out-of-bounds write vulnerability in the unistd::getgrouplist function. When a user belongs to more than 16 groups in /etc/groups, the function writes beyond the allocated buffer boundary, potentially allowing arbitrary code execution.
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
NixApplication
>= 0.16.0, < 0.20.2>= 0.21.0, < 0.21.2>= 0.22.0, < 0.22.2CVSS 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
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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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Identify nix crate as a dependencySearch for the nix crate in your project's Cargo.toml file or check Cargo.lock for nix entriesAffected if The nix crate is listed as a dependency in your project
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Check installed nix crate versionRun `cargo tree -p nix` or inspect the version specified in Cargo.lock under the nix crate entryAffected if The installed version falls within any of these ranges: >= 0.16.0 and < 0.20.2, or >= 0.21.0 and < 0.21.2, or >= 0.22.0 and < 0.22.2
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Verify getgrouplist function is usedSearch your source code for calls to getgrouplist, or grep for `getgrouplist` across your project filesAffected if Your code calls the getgrouplist function from the nix crate
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Check user group membership countRun `id` or `groups` command for the user who runs the application, or check /etc/group to count how many groups the user belongs toAffected if The user running the application belongs to more than 16 groups and uses vulnerable code paths
You are affected if the nix crate is a dependency with a vulnerable version (0.16.0 to <0.20.2, 0.21.0 to <0.21.2, or 0.22.0 to <0.22.2), your code calls getgrouplist, and the application runs with a user in more than 16 groups.
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 · scoped0.20.20.21.20.22.2
Upgrade the nix crate to version 0.20.2, 0.21.2, 0.22.2 or later to patch the out-of-bounds write in getgrouplist. Alternatively, audit code to ensure getgrouplist is not called with insufficient buffer allocation.
nix crate version 0.22.2 (or 0.21.2 / 0.20.2)
- Update the nix crate dependency in your Cargo.toml file to version 0.20.2, 0.21.2, or 0.22.2
- Run cargo update or cargo build to fetch the patched version
- Verify the update was applied correctly using cargo tree | grep nix
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Nix
Scoped from the published advisory
- Consultation2.0 h
- Implementation2.0 h
- Testing2.0 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 $1,984.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-45707 — 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-2021-45707 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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- Version or environment caveats, and links to real fixes
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