Vulnerability report

Exploited in the wild High confidence Not in CISA KEV

CVE-2021-32819

Remote code execution in squirrelly

Squirrellyjs / squirrelly · affected before 9.0.0

Watch CVE-2021-32819 Browse KEV feed
Severity
CVSS 8.0 · High
Confidence
High
Exploit status
Exploited in the wild
EPSS
58.3%
First observed
—
Last observed
—

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2021-32819 is an unauthenticated Remote code execution in squirrelly. Squirrelly is a template engine implemented in JavaScript that works out of the box with ExpressJS. Squirrelly mixes pure template data with...

Is it exploited?

Yes. Previdian tracks this CVE as a known exploited vulnerability. Confidence is high. Also confirmed by third-party sources.

Who is affected?

Squirrellyjs / squirrelly affected before 9.0.0.

What should we do?

Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.

Overview

Squirrelly is a template engine implemented in JavaScript that works out of the box with ExpressJS

Squirrelly is a template engine implemented in JavaScript that works out of the box with ExpressJS. Squirrelly mixes pure template data with engine configuration options through the Express render API. By overwriting internal configuration options remote code execution may be triggered in downstream applications.

This issue is fixed in version 9.0.0. For complete details refer to the referenced GHSL-2021-023.

squirrellyjs Affected
squirrelly
Before 9.0.0
Published
14 May 2021
Exploitation Reported
14 May 2021
Attack vector
Remote
Complexity
High
Privileges
None
User interaction
Required

Tags

nuclei_scanner

CVE References

Exploitation evidence

Why Previdian marks this CVE as exploited

Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.

Exploited in the wild

The Shadowserver

Recorded 14 May 2021

A trusted third party reported exploitation.

Proof of concept available

GitHub

Recorded 12 Jun 2021

Public scanner or PoC coverage increases practical exploitability.

Known exploited vulnerability sources

Per-source evidence links for KEV attestations are available through the Previdian Pro API.

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Source Added
The Shadowserver First 2021-05-14 00:00 UTC

Detection

Operational artifacts and observed signals

Make the evidence actionable in scanner, SOC, and edge-control workflows.

Observed signals

Request targets
User-Agents
Callback hosts
0
0
0

Request targets and User-Agents available in Pro. Callback host details available in Enterprise.

Virtual patch status

No Previdian virtual patch is currently available. Future rules ship for ModSecurity, Cloudflare, and AWS WAF.

Learn about virtual patches →

Scanner Artifacts

Scanner and exploit-framework references linked to this CVE.

Scanner Reference Detected
Nuclei https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2021/CVE-2021-32819.yaml 25 Apr 2025

Risk and context

Severity, weaknesses, and research context

CVSS v3.1

8.0 High

Potential damage if exploited. Separate from whether attackers are using it.

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:N

EPSS

58.3%

Estimated chance of exploitation in the next 30 days. Previdian's warning comes from evidence, not this score.

Weaknesses

Exposure of Sensitive Information to an Unauthorized Actor CWE-200

Potential Proof of Concepts

These PoCs are unverified and could contain malware. Use at your own risk.

Nodejs Squirrelly - Remote Code Execution

nuclei · Created Unknown

Timeline

From disclosure to observed exploitation

  1. 14:20 UTC

    Public PoC available

    Public proof-of-concept code published

  2. 00:00 UTC

    Nuclei template available

    Scanner coverage available

  3. 00:00 UTC

    Added to Previdian KEV Feed

    High-confidence, third-party attested exploitation

  4. 00:00 UTC

    CVE published

    Vulnerability disclosed publicly

  5. 00:00 UTC

    CVE ID reserved

    Identifier reserved by the CNA

Pro API

Automate this intelligence

Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.

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  • Evidence confidence and provenance
  • First-party sensor telemetry
  • PoC and scanner references
  • Affected versions and enrichment
  • Automation-ready JSON delivery

GET /api/v2/pro/kevs/CVE-2021-32819

Sample API response 
{
  "cve_id": "CVE-2021-32819",
  "confidence": "High",
  "cvss_score": 8.0,
  "cvss_estimated": false,
  "epss_score": 0.58286,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": false
  },
  "sensor_telemetry": { "attempts": 0, "sensors": 0 }
}