CVE-2026-106445 Handlebars - Server-Side Template Injection

Handlebars 4.0.0 to 4.7.10 contains a server-side template injection caused by lookupProperty returning Function.prototype.constructor before applying prototype-access deny list, letting attackers execute arbitrary JavaScript with server privileges, exploit requires allowProtoMethodsByDefault enabled and accessible function in template context.

CVSS base score 9.2 /10
Critical
CISA KEV
Not listed
Public exploit
Proof of concept available
Authentication
Not required
EPSS
0.41% chance of exploitation in 30 days
View the NVD record ↗

Details

Type
Server-Side Template Injection
Impact
Remote Code Execution
CVSS vector
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Published
6 October 2026
Updated
15 October 2026
Weakness
CWE-184

Vendor fix

Update to version 4.7.10 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

References

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