CVE-2026-33937
Handlebars provides the power necessary to let users build semantic templates. In versions 4.0.0 through 4.7.8, `Handlebars.compile()` accepts a pre-parsed AST object in addition to a template string. The `value` field of a `NumberLiteral` AST node is emitted directly into the generated JavaScript without quoting or sanitization. An attacker who can supply a crafted AST to `compile()` can therefore inject and execute arbitrary JavaScript, leading to Remote Code Execution on the server. Version 4.7.9 fixes the issue. Some workarounds are available. Validate input type before calling `Handlebars.compile()`; ensure the argument is always a `string`, never a plain object or JSON-deserialized value. Use the Handlebars runtime-only build (`handlebars/runtime`) on the server if templates are pre-compiled at build time; `compile()` will be unavailable.
- CVSS v3.1
- 9.8 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - CVSS v3.1
- 9.8 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - CVSS v3.1
- 9.8 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - EPSS
- 1.70% chance of exploitation in the next 30 days, 76th percentile
- Published
- 2026-03-27
- Updated
- 2026-08-31
Proof-of-concept exploits (5)
- advisories/GHSA-2w6w-674q-4c4q
- dinhvaren/cve-2026-339370★ · 2026-05-05
- EQSTLab/CVE-2026-339372★ · 2026-04-27
- garlic-wizard/CVE-2026-33937-for-DarkZeroReturns0★ · 2026-07-30
- c0gnit00/CVE-2026-339371★ · 2026-08-03