AlgorithmicaApplication · Algorithmica Project
CVE-2021-31996
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 algorithmica crate through 2021-03-07 for Rust. There is a double free in merge_sort::merge().
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 confidenceThe algorithmica Rust crate through 2021-03-07 contains a double free vulnerability in the merge_sort::merge() function. A double free occurs when memory is deallocated twice, leading to heap corruption, undefined behavior, and potential code execution exploits.
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
AlgorithmicaApplication
<= 2021-03-07CVSS 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
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/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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Check Cargo.toml for algorithmica dependencyInspect your project's Cargo.toml file for 'algorithmica' under [dependencies] or [dev-dependencies] sectionsAffected if algorithmica is listed as a dependency with version <= 2021-03-07 or without an upper version limit
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Check Cargo.lock for algorithmica versionLook in Cargo.lock for the [[package]] entry named 'algorithmica' and note the 'version' fieldAffected if The version field shows 2021-03-07 or earlier, or shows a version without a fix commit hash
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Check for merge_sort usage in source codeSearch your Rust source files for 'use algorithmica::merge_sort' or 'algorithmica::merge_sort::merge' imports or function callsAffected if The merge_sort module from algorithmica is imported and called in your code
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Check crate source for vulnerable functionIf algorithmica is a local or vendored dependency, inspect the src/merge_sort.rs file and locate the merge() function to see if it contains the double-free defect patternAffected if The merge() function contains code that frees the same pointer twice (e.g., free in both normal and error paths without nullifying the pointer)
You are affected if the algorithmica crate version is <= 2021-03-07 and your code uses the merge_sort::merge() function.
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.
From vendor dataUpdate to a patched version of the algorithmica crate when available, or replace the merge_sort implementation with a safe alternative from a maintained crate.
Fix this in Algorithmica
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,328.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-31996 — 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-2021-31996 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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