handlebars-lang

CVE-2026-106446: Handlebars: JavaScript Injection via AST Type Confusion in compile (Program.blockParams)

Is it exploited?

Not on CISA's list. CISA has not added it to the Known Exploited Vulnerabilities catalog as of 28 Oct 2026. If CISA adds it, this page shows it as known exploited.

How likely is exploitation in the next 30 days?

0.8%

EPSS score, percentile 56 of all scored records. A probability estimated by FIRST, not a report of exploitation.

CISA's SSVC assessment in the CVE record lists exploitation as poc.

How severe?

9.8 Critical

CVSS v3.1 base score, given by the CNA

What should I do?

CISA has set no required action, because the vulnerability is not in KEV.

The CVE record links no vendor advisory, patch or mitigation.

Which versions are affected?

Affected

>= 4.0.0, < 4.7.10

Versions by product

Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 29 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-29_0000Z, as of 29 Oct 2026. About the data.

What to do

Advisories and patches

The CVE record links no vendor advisory, patch or mitigation.

Affected products and versions

As listed in the CVE record.

handlebars-lang handlebars.js
Status	Versions
Affected	>= 4.0.0, < 4.7.10

Source: CVE List V5 (CVE Program), cve_2026-10-29_0000Z, as of 29 Oct 2026. About the data.

About this vulnerability

Summary: CVE record, as of 29 Oct 2026.

CISA has not added CVE-2026-106446 to its Known Exploited Vulnerabilities (KEV) catalog, as of 28 Oct 2026.
The CVE record was published on 6 Oct 2026.
The CVE record carries a CVSS v3.1 base score of 9.8 (Critical), given by its CNA.
FIRST's EPSS model puts the probability of exploitation in the next 30 days at 0.8% (percentile 56), as of 29 Oct 2026. EPSS is a statistical estimate, not a report of exploitation.
CISA's SSVC assessment in the CVE record: exploitation poc, automatable yes, technical impact total.

Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-29_0000Z, as of 29 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 29 Oct 2026. About the data.

Description

Handlebars: JavaScript Injection via AST Type Confusion in compile (Program.blockParams)

Handlebars provides the power necessary to let users build semantic templates. From 4.0.0 until 4.7.10, Handlebars.compile() and Handlebars.precompile() accept pre-parsed AST objects while validating only selected PathExpression, NumberLiteral, and BooleanLiteral values. This issue bypasses the AST validation introduced in version 4.7.9 for CVE-2026-33937. An attacker who can supply an object instead of a template string can place JavaScript expressions in unchecked values such as Program.blockParams.length, a non-PathExpression parameter depth, a non-string StringLiteral.value, or a non-string PathExpression.original. The compiler emits those values into generated JavaScript, causing code execution in the server process when compile output renders or wherever precompile output is loaded. Applications that pass only template strings are not affected. This issue is fixed in version 4.7.10.

Source: CVE List V5 (CVE Program), cve_2026-10-29_0000Z, as of 29 Oct 2026. About the data.

Weakness

CWE-94: Improper Control of Generation of Code ('Code Injection')
CWE-843: Access of Resource Using Incompatible Type ('Type Confusion')

CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record.

Timeline

Date	Event
6 Oct 2026	CVE record published
7 Oct 2026	CVE record last updated