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Review reviewHigh

CVE-2026-33940

handlebars-lang handlebars.js, Cluster Observability Operator 1.5.0, Red Hat OpenShift Dev Spaces 3.27

Handlebars provides the power necessary to let users build semantic templates. In versions 4.0.0 through 4.7.8, a crafted object placed in the template context can bypass all conditional guards in `resolvePartial()` and cause `invokePartial()` to return `undefined`. The Handlebars runtime then treats the unresolved partial as a source that needs to be compiled, passing the crafted object to `env.compile()`. Because the object is a valid Handlebars AST containing injected code, the generated JavaScript executes arbitrary commands on the server. The attack requires the adversary to control a...

CVSS
8.1
EPSS
0.70%
49.7% percentile
CISA KEV
Not listed
Published
2026.03.28
PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV
Exploit probability0.70%
Technical severityCVSS 8.1

Vulnerability overview

Handlebars provides the power necessary to let users build semantic templates. In versions 4.0.0 through 4.7.8, a crafted object placed in the template context can bypass all conditional guards in `resolvePartial()` and cause `invokePartial()` to return `undefined`. The Handlebars runtime then treats the unresolved partial as a source that needs to be compiled, passing the crafted object to `env.compile()`. Because the object is a valid Handlebars AST containing injected code, the generated JavaScript executes arbitrary commands on the server. The attack requires the adversary to control a...

Affected product and versions

Product
handlebars-lang handlebars.js, Cluster Observability Operator 1.5.0, Red Hat OpenShift Dev Spaces 3.27
Affected versions
>= >= 4.0.0, < 4.7.9, >= 4.0.0 < 4.7.9
Fixed versions
4.7.9

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide
  1. 1
    Identify

    Confirm that handlebars-lang handlebars.js, Cluster Observability Operator 1.5.0, Red Hat OpenShift Dev Spaces 3.27 and an affected version are present.

  2. 2
    Prioritize

    Combine exploitation signals with asset exposure and business criticality.

  3. 3
    Remediate

    Follow the vendor advisory or supported update path and preserve rollback options.

  4. 4
    Verify

    Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
CWE
CWE-843, CWE-94