Code Injection in Handlebarsjs (CVE-2026-33937)
Summary
Code injection in Handlebarsjs (CVE-2026-33937). Successful exploitation can lead to full system takeover. Exploitable via value.
Original description
The description as published by the source.
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.
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-33937 has been found in Handlebarsjs.
Attackers can target a specific entry point like value over the network to misuse the product.
Successful exploitation can lead to full system takeover. CVSS score: 9.8/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Handlebarsjs CVE-2026-33937" on the vendor's site.
CVE-2026-33937 (Handlebarsjs) — CWE-94 / CVSS v3 9.8
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: value / NumberLiteral / string
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
Arbitrary code execution (CWE-94) exists in Handlebarsjs. Attackers reach the vulnerable code path via value without authentication.
Check the vendor advisory for the affected versions of Handlebarsjs. Attack surface: value / NumberLiteral / string.
Severity: Critical (CVSS 9.8/10). Successful exploitation can lead to full system takeover.
Update to the patched release per vendor advisory.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'Handlebarsjs' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'Handlebarsjs' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
Handlebarsjsを grep し、稼働しているサービス・バージョンを把握する。 -
2Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2026-33937 node-handlebars
- Ubuntu UBUNTU-CVE-2026-33937 node-handlebars
References
- advisory github.com
- advisory access.redhat.com
- advisory access.redhat.com
- advisory access.redhat.com
- advisory github.com
- advisory nvd.nist.gov
- patch github.com
- report bugzilla.redhat.com
- web github.com
- web security.access.redhat.com