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NVD / CVE Program· CNA GitHub_M

CVE-2026-33941: Handlebars.js has JavaScript Injection in CLI Precompiler via Unescaped Names and Options

Noroxi assessment

Priority: Monitor (action score 32/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.29% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. A user must open a link or visit a page. No special conditions are required; it is repeatable.
  • Fixed version: node-handlebars (Debian:14) 3:4.7.9-1; handlebars (npm) 4.7.9.

Low priority for now. Upgrade to node-handlebars (Debian:14) 3:4.7.9-1; handlebars (npm) 4.7.9 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

Handlebars provides the power necessary to let users build semantic templates. In versions 4.0.0 through 4.7.8, the Handlebars CLI precompiler (`bin/handlebars` / `lib/precompiler.js`) concatenates user-controlled strings — template file names and several CLI options — directly into the JavaScript it emits, without any escaping or sanitization. An attacker who can influence template filenames or CLI arguments can inject arbitrary JavaScript that executes when the generated bundle is loaded in Node.js or a browser. Version 4.7.9 fixes the issue. Some workarounds are available. First, validate all CLI inputs before invoking the precompiler. Reject filenames and option values that contain characters with JavaScript string-escaping significance (`"`, `'`, `;`, etc.). Second, use a fixed, trusted namespace string passed via a configuration file rather than command-line arguments in automated pipelines. Third, run the precompiler in a sandboxed environment (container with no write access to sensitive paths) to limit the impact of successful exploitation. Fourth, audit template filenames in any repository or package that is consumed by an automated build pipeline.

HighCVSS 8.2 · v3.1—No exploit Fix available
Published
Mar 27, 2026
Updated
Oct 26, 2026
EPSS
0.2% · 22th percentile

Report tools

JSON

Action score

32

Monitor

Low priority for now.

CVSS
32 / 40 · 8.2 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.2%

CISA SSVC decision

Exploitation
proof of concept
Automatable
no
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
8.2
CNA · GitHub_M
8.2
agree

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

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When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
handlebarsjshandlebars

Is the Handlebars on your site affected?

The free JavaScript library scanner reads the Handlebars version from the files your site loads, matches this record and other known vulnerabilities, and gives the safe version on the same branch. If the version can't be read, it says so. No account needed.

Scan JavaScript libraries

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • handlebarsjs handlebars4.0.0 and later · before 4.7.9

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

  • handlebars-lang handlebars.js

    • >= 4.0.0, < 4.7.9affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12node-handlebarsfrom 0—
Debian:14node-handlebarsbefore 3:4.7.9-13:4.7.9-1
npmhandlebarsfrom 4.0.0 · before 4.7.94.7.9

Same product

handlebarsjs: all records

Other highest-scoring records for the same primary product.

  • CVE-2021-23369Remote Code Execution (RCE)
    41Plan
  • CVE-2026-33937Handlebars.js has JavaScript Injection via AST Type Confusion
    40Plan
  • CVE-2021-23383The package handlebars before 4.7.7 are vulnerable to Prototype Pollution when selecting certain compiling options to compile templates comi
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2026-33938Mar 27, 2026 · Handlebars.js has JavaScript Injection via AST Type Confusion by tampering @partial-block
    32Monitor
  • ← EarlierCVE-2026-33939Mar 27, 2026 · Handlebars.js has Denial of Service via Malformed Decorator Syntax in Template Compilation
    30Monitor
  • ← EarlierCVE-2026-33940Mar 27, 2026 · Handlebars.js has JavaScript Injection via AST Type Confusion when passing an object as dynamic partial
    32Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
debian:node-handlebars3:4.7.9-1 · Debian:14Package registry (OSV)
npm:handlebars4.7.9Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-339160 days apartHandlebars.js has Prototype Pollution Leading to XSS through Partial Template Injection
    18Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • A user must open a link or visit a page.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted

Impact can extend beyond the vulnerable component (scope changes).

Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
Required
Scope
Changed
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H

nvd-primary

Root cause

User content is inserted into the page as HTML. The browser interprets the content as code rather than data.

The bug in code

The whole CWE-79 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

ts
commentEl.innerHTML = comment.body;

Fixed

ts
commentEl.textContent = comment.body;

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

  1. Fix✗ → ✓

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References

Show all references (6 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records