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TI-2026-26288 Aliases CVE-2026-33937GHSA-2w6w-674q-4c4q

Handlebars.js has JavaScript Injection via AST Type Confusion

Priority HIGH 82CWE-843Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Code execution
Confidentiality · integrity · availability
High · High · High
Fix status
Partial Red Hat: 2 fixed, 5 without a fix

Attack profile from CVSS 3.1 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-843 and the CVSS impact.

Summary

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.01907 79th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Partial handlebars.js (handlebars-lang): 4.7.9handlebars (npm): 4.7.9Red Hat: 2 advisoriesRed Hat: 2 fixed, 5 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
Yes
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
handlebars-langhandlebars.js4.0.0 to before 4.7.94.7.9Patch availableCNA
—handlebars (npm)4.0.0 to before 4.7.94.7.9Patch availableGHSA-2w6w-674q-4c4q
  • handlebars.js Vendorhandlebars-lang Affected 4.0.0 to before 4.7.9 Fixed in 4.7.9 Patch available CNA
  • handlebars (npm) Vendor— Affected 4.0.0 to before 4.7.9 Fixed in 4.7.9 Patch available GHSA-2w6w-674q-4c4q

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:handlebarsjs:handlebars:*:*:*:*:*:node.js:*:*4.0.0 to before 4.7.9Vulnerablehandlebars-lang
  • cpe:2.3:a:handlebarsjs:handlebars:*:*:*:*:*:node.js:*:* Versions 4.0.0 to before 4.7.9 Vulnerable ·handlebars-lang

Remediation

  • Fix · CNA handlebars.js (handlebars-lang) Fixed in 4.7.9
  • Fix · GHSA-2w6w-674q-4c4q handlebars (npm) Fixed in 4.7.9 Advisory →

Red Hat 2 advisories

  • RHSA-2026:34342 Released 2026-07-01 · Red Hat rating Critical
    Cluster Observability Operator 1.5.0
    • Cluster Observability Operator 1.5 registry.redhat.io/cluster-observability-operator/distributed-tracing-console-plugin-pf4-rhel9, registry.redhat.io/cluster-observability-operator/distributed-tracing-console-plugin-pf5-rhel9, registry.redhat.io/cluster-observability-operator/distributed-tracing-console-plugin-pf6-rhel9 +9
  • RHSA-2026:10175 Released 2026-04-23 · Red Hat rating Important
    Red Hat OpenShift Dev Spaces 3.27.1 Release.
    • Red Hat OpenShift Dev Spaces 3.27 registry.redhat.io/devspaces/code-rhel9, registry.redhat.io/devspaces/dashboard-rhel9, registry.redhat.io/devspaces/devspaces-rhel9-operator +8

Vendor assessments

Red Hat

Red Hat rating: Important. Red Hat's page for this CVE →

ProductStatusPlan or fix
Logging Subsystem for Red Hat OpenShiftAffectedNo fix planned: Will not fix
Red Hat Developer Hub 1AffectedNo fix yet
Red Hat Enterprise Linux 10AffectedNo fix yet
Red Hat Enterprise Linux 8AffectedNo fix yet
Red Hat Enterprise Linux 9AffectedNo fix yet
Cluster Observability Operator 1.5Fixed RHSA-2026:34342
Red Hat OpenShift Dev Spaces 3.27Fixed RHSA-2026:10175
Not affected: 11 products
  • Cluster Observability Operator 1.5
  • Cryostat 4
  • Red Hat Data Grid 8
  • Red Hat Enterprise Linux 10
  • Red Hat Enterprise Linux 7
  • Red Hat Enterprise Linux 8
  • Red Hat Enterprise Linux 9
  • Red Hat OpenShift AI (RHOAI)
  • Red Hat OpenShift Dev Spaces
  • Red Hat OpenShift Dev Spaces 3.27
  • Red Hat Process Automation 7

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-33937
  2. 2026-10-03 Alias added: GHSA-2w6w-674q-4c4q
  3. 2026-10-18 Fix available: Cluster Observability Operator 1.5.3 · Red Hat
  4. 2026-10-27 Affected versions changed · Red Hat
  5. 2026-11-05 Fix available: Cluster Observability Operator 1.5 · Red Hat

References

Exploit 1

Patch 1

Advisory 1

Other 2

  • TI-2026-26290 Handlebars.js has Denial of Service via Malformed Decorator Syntax in Template Compilation CVSS 3.1HIGH 7.5
  • TI-2026-26292 Handlebars.js has JavaScript Injection in CLI Precompiler via Unescaped Names and Options CVSS 3.1HIGH 8.3
  • TI-2026-26291 Handlebars.js has JavaScript Injection via AST Type Confusion when passing an object as dynamic partial CVSS 3.1HIGH 8.1
  • TI-2026-26289 Handlebars.js has JavaScript Injection via AST Type Confusion by tampering @partial-block CVSS 3.1HIGH 8.1
  • TI-2021-06062 Remote code execution (RCE) in handlebars CVSS 3.1CRITICAL 9.8
  • TI-2021-06076 Prototype pollution in handlebars CVSS 3.1CRITICAL 9.8
See all 9 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences