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CVE-2026-33939 high CVSS 7.5

Vulnerability in Handlebarsjs (CVE-2026-33939)

Summary

Vulnerability in Handlebarsjs (CVE-2026-33939). Risk of unauthorized operations or information disclosure. Exploitable via undefined.

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, when a Handlebars template contains decorator syntax referencing an unregistered decorator (e.g. {{*n}}), the compiled template calls lookupProperty(decorators, "n"), which returns undefined. The runtime then immediately invokes the result as a function, causing an unhandled TypeError: ... is not a function that crashes the Node.js process. Any application that compiles user-supplied templates without wrapping the call in a try/catch is vulnerable to a single-request Denial of Service. Version 4.7.9 fixes the issue. Some workarounds are available. Wrap compilation and rendering in try/catch. Validate template input before passing it to compile(); reject templates containing decorator syntax ({{*...}}) if decorators are not used in your application. Use the pre-compilation workflow; compile templates at build time and serve only pre-compiled templates; do not call compile() at request time.

Source: NIST National Vulnerability Database NVD

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-2026-33939 has been found in Handlebarsjs.
Attackers can target a specific entry point like undefined over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Handlebarsjs CVE-2026-33939" on the vendor's site.

CVE-2026-33939 (Handlebarsjs) — CWE-754 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: undefined
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.

❓ What is the problem

A vulnerability (CWE-754) exists in Handlebarsjs. Attackers reach the vulnerable code path via undefined without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of Handlebarsjs. Attack surface: undefined.

🔥 Severity

Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to the patched release per vendor advisory.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

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

  1. 1
    Identify 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。

  2. 2
    Post-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

References

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