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CVE Record

CVE-2019-20920: Handlebars before 3.0.8 and 4.x before 4.5.3 is vulnerable to Arbitrary Code Execution.

Handlebars before 3.0.8 and 4.x before 4.5.3 is vulnerable to Arbitrary Code Execution. The lookup helper fails to properly validate templates, allowing attackers to submit templates that execute arbitrary JavaScript. This can be used to run arbitrary code on a server processing Handlebars templates or in a victim's browser (effectively serving as XSS).

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

Handlebars versions before 3.0.8 and 4.x before 4.5.3 could process a malicious template in a way that executes JavaScript. If a server accepts attacker-controlled Handlebars templates, this may become server-side code execution. In browser rendering contexts, it can act like cross-site scripting.

Executive priority

Prioritize remediation where Handlebars runs server-side or handles tenant-controlled templates. If Handlebars is only used with trusted, static templates, urgency is lower but dependency upgrades remain appropriate.

Technical view

The source bundle attributes the flaw to improper validation in the Handlebars lookup helper. Attackers who can submit templates may trigger arbitrary JavaScript execution during template processing. The affected version ranges named are before 3.0.8 and 4.x before 4.5.3.

Likely exposure

Exposure is most likely in JavaScript applications or build pipelines using vulnerable Handlebars versions, especially where users, tenants, CMS authors, or integrations can provide templates rather than only data.

Exploitation context

The bundle does not cite active exploitation and KEV is false. Practical risk depends on whether attackers can influence Handlebars templates processed by the application or delivered to users.

Researcher notes

The public bundle is sparse: no CVSS, CWE, CPE, or exploit confirmation is provided. Analysis should focus on template trust boundaries, dependency resolution, and whether affected versions are reachable in deployed code.

Mitigation direction

  • Upgrade Handlebars to 3.0.8, 4.5.3, or a later supported version.
  • Audit direct and transitive dependencies for vulnerable Handlebars versions.
  • Do not process untrusted user-supplied templates without strong isolation and review.
  • Check vendor advisories for version-specific upgrade guidance.

Validation and detection

  • Review package manifests and lockfiles for Handlebars versions below fixed releases.
  • Identify code paths that compile templates from user, tenant, CMS, or integration input.
  • Confirm deployed artifacts use the upgraded dependency, not only source manifests.
  • Review dependency scanner results against the referenced npm and Snyk advisories.
Prepared
Confidence
medium
Sources
5

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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Execution behavior lookup

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CVE-2019-20920 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
4Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

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