CVE-2026-59880
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 · uneditedImmutable.js provides many Persistent Immutable data structures. Prior to 4.3.9 and 5.1.8, Immutable.Map and Immutable.Set keep keys that share the same 32-bit hash in a HashCollisionNode collision bucket that is scanned linearly, allowing an attacker who controls keys inserted into a Map, such as through Immutable.Map(obj), Immutable.fromJS(obj), state.merge(userObject), or mergeDeep, to craft many colliding keys and degrade insertion and lookup to consume disproportionate CPU. This issue is fixed in versions 4.3.9 and 5.1.8.
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 confidenceImmutable.js HashCollisionNode uses linear scanning for keys with matching 32-bit hashes. An attacker controlling keys inserted via Immutable.Map(), Immutable.fromJS(), merge(), or mergeDeep() can craft many hash-colliding keys to cause disproportionate CPU consumption during insert and lookup operations, creating a denial-of-service vulnerability.
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< 4.3.9>= 5.0.0, < 5.1.8CVSS 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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Identify Immutable.js installation and versionCheck your package.json or node_modules/immutable/package.json for the installed version. Run 'npm list immutable' or 'yarn list immutable' to see the resolved version.Affected if The installed version is less than 4.3.9 OR is 5.0.0 through 5.1.7 (inclusive)
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Detect usage of vulnerable collection constructorsSearch your codebase for calls to Immutable.Map(), Immutable.fromJS(), merge(), or mergeDeep() that accept external or user-supplied input as keys.Affected if Your application passes user-controlled objects or keys to any of these methods without prior validation
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Determine if keys could be attacker-controlledReview the data flow leading to the affected methods. Check if keys originate from HTTP requests, API inputs, file uploads, or other untrusted sources.Affected if Keys inserted into Immutable collections can be set by an external attacker rather than being hardcoded or generated internally from trusted sources
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Check for HashCollisionNode trigger conditionsMonitor or inspect your application behavior when inserting many records with potentially similar or crafted keys. The vulnerability is triggered when multiple keys share the same 32-bit hash value.Affected if Your application routinely inserts collections where an attacker could supply many keys designed to produce hash collisions
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Audit logging for CPU spikes during collection operationsIf already deployed, review application logs and monitoring for unusual CPU consumption correlating with collection insert or lookup operations involving external input.Affected if CPU consumption spikes occur during Immutable.js merge or insert operations with user-supplied keys, indicating potential exploitation
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Verify if the vulnerable code path is reachableTrace which Immutable.js methods are actually called at runtime and whether the code paths involving HashCollisionNode (triggered by hash-colliding keys) are exercised.Affected if The vulnerable linear-scan code path in HashCollisionNode can be reached through your specific usage patterns
You are affected if your installed Immutable.js version falls outside the fixed ranges (below 4.3.9 or 5.0.0-5.1.7) AND your application accepts external or user-controlled keys to be inserted via Map(), fromJS(), merge(), or mergeDeep() methods.
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 · scoped4.3.95.1.8
Upgrade Immutable.js to version 4.3.9 or 5.1.8 or later. If upgrade is not immediately feasible, validate and sanitize any user-controlled objects before passing them to Immutable.js collection constructors or merge methods.
immutable-js version 4.3.9 or 5.1.8 (or later compatible versions)
- Identify the current version of immutable-js in use (check package.json or package-lock.json)
- If using immutable-js 4.x, upgrade to version 4.3.9 or later: npm install immutable@^4.3.9
- If using immutable-js 5.x, upgrade to version 5.1.8 or later: npm install immutable@^5.1.8
- Run tests to verify the upgrade does not break existing functionality
- Rebuild and redeploy the application
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation2.0 h
- Testing4.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-59880 — 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-2026-59880 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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