CVE-2026-33937
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 · uneditedHandlebars provides the power necessary to let users build semantic templates. In versions 4.0.0 through 4.7.8, `Handlebars.compile()` accepts a pre-parsed AST object in addition to a template string. The `value` field of a `NumberLiteral` AST node is emitted directly into the generated JavaScript without quoting or sanitization. An attacker who can supply a crafted AST to `compile()` can therefore inject and execute arbitrary JavaScript, leading to Remote Code Execution on the server. Version 4.7.9 fixes the issue. Some workarounds are available. Validate input type before calling `Handlebars.compile()`; ensure the argument is always a `string`, never a plain object or JSON-deserialized value. Use the Handlebars runtime-only build (`handlebars/runtime`) on the server if templates are pre-compiled at build time; `compile()` will be unavailable.
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 confidenceHandlebars.js versions 4.0.0-4.7.8 has a Remote Code Execution vulnerability where the `Handlebars.compile()` function accepts pre-parsed AST objects in addition to template strings. The `value` field of a `NumberLiteral` AST node is emitted directly into generated JavaScript without quoting or sanitization, allowing attackers who control the AST input to inject and execute arbitrary JavaScript code on the server.
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>= 4.0.0, < 4.7.9CVSS 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.
-
Check installed Handlebars versionRun `npm list handlebars` or inspect package.json to see the exact version number installedAffected if Version is 4.0.0 through 4.7.8 (anything < 4.7.9)
-
Identify Handlebars.compile() usageSearch codebase for calls to `Handlebars.compile(` or `require('handlebars').compile(` patternsAffected if Any usage of compile() is found in the codebase
-
Inspect compile() input typesReview all compile() call sites and determine if any pass objects (AST) rather than template strings; look for patterns like compile(astObject) or compile(JSON.parse(...))Affected if compile() receives plain objects or parsed JSON as input rather than only string templates
-
Check for NumberLiteral AST handlingIf compile() receives AST objects, examine whether NumberLiteral node objects with a `value` field are constructed or passed in; search for patterns involving number literals in AST generationAffected if Code constructs or deserializes AST objects containing NumberLiteral nodes that could supply a malicious `value` field to compile()
You are affected if Handlebars version is < 4.7.9 AND your code passes non-string objects (especially AST structures with NumberLiteral nodes) to the compile() 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.
dbcve · scoped4.7.9
Upgrade Handlebars to version 4.7.9 or later. As a workaround, validate that the argument to `compile()` is always a string before calling it, or use the runtime-only build (`handlebars/runtime`) which does not expose the `compile()` function.
Handlebars version 4.7.9 or later
- Upgrade Handlebars to version 4.7.9 or later using your package manager (e.g., npm install [email protected] or npm install handlebars@latest)
- After upgrading, test your application to ensure templates compile and render correctly
- As an additional defense-in-depth measure, add input validation before calling Handlebars.compile() to ensure the argument is always a string, never a plain object or JSON-deserialized value
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation3.0 h
- Implementation2.0 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 $2,544.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-33937 — 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-2026-33937 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
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
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.
- 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