CVE-2026-106446: Code Injection (CVSS 9.8)

Description

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.

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CVSS v3.1 Score

9.8

CRITICAL

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

EPSS — Exploit Prediction

0.0064

Probability of exploitation

0.50%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-94 CWE-94

CWE-843 CWE-843

References

Other References

https://github.com/handlebars-lang/handlebars.js/commit/703fdcc5fd6cc8d1cc0c33cc19de40c467c4b8d2 https://github.com/handlebars-lang/handlebars.js/pull/2185 https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.10 https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-8r5x-fm3f-whwj https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-8r5x-fm3f-whwj

Frequently Asked Questions

What is CVE-2026-106446? +

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. It has a CVSS v3.1 base score of 9.8 (CRITICAL).

How severe is CVE-2026-106446? +

CVE-2026-106446 has a CVSS v3.1 score of 9.8 out of 10, rated CRITICAL. This is a critical vulnerability that should be patched immediately. The EPSS score is 0.0064, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-106446? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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