CVE Intelligence
High Cross-site scripting exploit reference

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

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.

Published Mar 27, 2026 · Updated Oct 13, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: GitHub_M

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.
How the score was calculated
  • EPSS 0.2% (30-day exploitation probability)+2
  • Technical severity (high)+6
  • CISA SSVC: exploitation "poc"+5

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Not confirmed
Not in CISA KEV — an absence of record, not proof it is unexploited.
EPSS FIRST
0.22%
ahead of 12% of scored CVEs · Oct 14, 2026
Affects
Handlebars-lang
Handlebars.js and 1 more
CVSS base
8.2
High · 4 source(s)
Prioritization reference: 8.3 provisional

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation
Proof of concept
none · proof-of-concept · active
Automatable
No
can an attacker script the kill-chain steps
Technical impact
Total
partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

  • Documented patch — github.com (NIST National Vulnerability Database)

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (Handlebars-lang Handlebars.js, Handlebarsjs Handlebars).
  2. Apply the fixed version or the patch documented under Remediation.
  3. Exploitation requires user interaction: tighten email/web filtering and warn affected users.
  4. Search available logs for exploit probes matching the vulnerability class (cross-site scripting), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Handlebars-lang Handlebars.js version >= 4.0.0, < 4.7.9 Vulnerable CVE Program (cve.org) e CISA ADP
Handlebarsjs Handlebars ≥ 4.0.0 and < 4.7.9 Vulnerable NIST National Vulnerability Database

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

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

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
8.3 CVSS 3.1 High — — GitHub_M via CVE Program (cve.org) e CISA ADP
8.2 CVSS 3.1 High 1.5 6.0 security-advisories@github.com via NIST National Vulnerability Database
8.2 CVSS 3.1 High 1.5 6.0 nvd@nist.gov via NIST National Vulnerability Database
8.2 CVSS 3.1 High 1.5 6.0 0b0ca135-0b70-47e7-9f44-1890c2a1c46c via NIST National Vulnerability Database
CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H (score shown at the top: nvd@nist.gov)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-79 · Cross-site Scripting (XSS)

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.22%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Local/physical vector: focus on endpoint telemetry (EDR) from affected hosts.
  • Monitor CSP violation reports and script payloads in reflected parameters.
endpoint telemetry (EDR)web/proxy/WAF logsapplication logs

Timeline

What happened to this CVE, newest first.

  • 2026
  • Affected products added · handlebars-lang/handlebars.js
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • SSVC assessment updated
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 13, 2026
  • Fix documented
    Oct 13, 2026 · NIST National Vulnerability Database
  • CVSS changed · 8.2
    Oct 13, 2026 · NIST National Vulnerability Database
  • Source status changed · → Modified
    Oct 13, 2026 · NIST National Vulnerability Database
  • Record created in this database
    Oct 13, 2026 · NIST National Vulnerability Database
  • CVE published
    Mar 27, 2026 · GitHub_M

Source activity

Repeated readings are counted rather than listed.

  • 1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

8 on the record

Elsewhere on this site

Handlebars-lang
every CVE for this vendor
Cross-site scripting
same class
CWE-79
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-106446 Handlebars: JavaScript Injection via AST Type Confusion in compile (Program.blockParams) 9d
  • CVE-2026-106444 Handlebars: JavaScript Injection via Unsafe Inline Embedding of Precompiled Templates 9d
  • CVE-2026-106445 Handlebars: JavaScript Injection via Own Property Check Bypass 9d
  • CVE-2026-33940 Handlebars.js has JavaScript Injection via AST Type Confusion when passing an object as dynamic partial Mar 27, 2026
  • CVE-2026-33939 Handlebars.js has Denial of Service via Malformed Decorator Syntax in Template Compilation Mar 27, 2026
  • CVE-2026-33916 Handlebars.js has Prototype Pollution Leading to XSS through Partial Template Injection Mar 27, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-33941 is "Handlebars.js has JavaScript Injection in CLI Precompiler via Unescaped Names and Options", rated High. It affects Handlebars.js (Handlebars-lang); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 8.2 describes technical severity. EPSS 0.22% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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