Vulnerability report

Exploited in the wild High confidence Not in CISA KEV

CVE-2026-42796

Arelle Remote Code Execution

Arelle / Arelle · affected before 2.39.10

View live feed Monitor via API Watch CVE-2026-42796
Severity
CVSS 9.2 · Critical
Confidence
High
Exploit status
Exploited in the wild
EPSS
2.7%
First observed
—
Last observed
—

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2026-42796 is an unauthenticated vulnerability affecting Arelle Arelle. Arelle before 2.39.10 contains an unauthenticated remote code execution vulnerability in the /rest/configure REST endpoint that accepts a...

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?

Arelle / Arelle affected before 2.39.10.

What should we do?

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

Overview

Arelle Remote Code Execution

Arelle before 2.39.10 contains an unauthenticated remote code execution vulnerability in the /rest/configure REST endpoint that accepts a plugins query parameter and forwards it to the plugin manager without authentication or authorization.

Attackers can supply a URL to a malicious Python file through the plugins parameter, causing the Arelle webserver to download and execute the attacker-controlled code within the Arelle process with its privileges.

Arelle Affected
Arelle
Before 2.39.10
View vendor advisory (opens in new tab)
Published
04 May 2026
Exploitation Reported
18 Sep 2026
Attack vector
Remote
Complexity
Low
Privileges
None
User interaction
None

Tags

python

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 18 Sep 2026

A trusted third party reported exploitation.

Proof of concept available

Nuclei Templates

Recorded 24 Jul 2026

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.

Learn about Pro API access
Source Added
The Shadowserver First 2026-09-18 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/2026/CVE-2026-42796.yaml 24 Jul 2026

Risk and context

Severity, weaknesses, and research context

CVSS v4.0

9.2 Critical
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

EPSS

2.7%

Weaknesses

Missing Authentication for Critical Function CWE-306

All CVSS Scores

CVSS v4.0 9.2 Critical

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

CVSS v3.1 9.8 Critical

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

Potential Proof of Concepts

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

Arelle < 2.39.10 - Remote Code Execution

nuclei · Created Unknown

Timeline

From disclosure to observed exploitation

  1. 00:00 UTC

    Added to Previdian KEV Feed

    High-confidence, third-party attested exploitation

  2. 04:32 UTC

    Public PoC available

    Public proof-of-concept code published

  3. 04:32 UTC

    Nuclei template available

    Scanner coverage available

  4. 17:19 UTC

    CVE published

    Vulnerability disclosed publicly

  5. 20:58 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.

View Pro pricing Read API docs
  • 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-2026-42796

Free JSON includes basic KEV fields 
{
  "cve_id": "CVE-2026-42796",
  "confidence": "High",
  "cvss_score": 9.2,
  "cvss_estimated": false,
  "epss_score": 0.02747,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": false
  },
  "sensor_telemetry": { "attempts": 0, "sensors": 0 }
}