GHSA-p8wg-vrv2-v86f: handlebars (CVE-2026-106445)

Package	Ecosystem	Affected	Fixed in
handlebars	npm	>=3.0.0, <4.7.10	4.7.10

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

Handlebars versions from 3.0.0 before 4.7.10 are affected. An attacker who can get a controlled template rendered with allowProtoMethodsByDefault set to true can bypass the prototype-access deny list and reach the Function constructor, which allows arbitrary JavaScript execution and possible remote code execution on the server. Upgrade Handlebars to 4.7.10 or later; until then, do not enable allowProtoMethodsByDefault when rendering untrusted templates with untrusted data.

Written 31 Oct 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

Score	Rating	CVSS	Vector	Source
9.2	Critical	4.0	CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N	CNA (GitHub_M)

CISA KEV Not listed.
EPSS 0.0059, the 48th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

31 Oct 2026, 13:33 UTC First seen by agentprime
31 Oct 2026, 13:33 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.