Vulnerability report

Trusted Third Party Report High Confidence Not in CISA KEV

CVE-2026-42796

Arelle Remote Code Execution

Arelle · affected before 2.39.10

Watch CVE-2026-42796 Browse KEV feed
Severity
CVSS 9.2 · Critical
Confidence
High
Exploit status
Trusted Third Party Report
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.

Have exploitation attempts been observed?

Yes. Exploitation attempts have been reported for this vulnerability. Previdian lists it as a known exploited vulnerability. Also reported by third-party sources. Confidence is high.

Who is affected?

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 Attempts Reported
18 Sep 2026
Attack vector
Remote
Complexity
Low
Privileges
None
User interaction
None

Tags

python nuclei_scanner

CVE References

Exploitation evidence

Evidence of exploitation attempts

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

Exploitation Attempts Observed in the Wild

The Shadowserver

Recorded 18 Sep 2026

A trusted third party reported exploitation attempts.

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.

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

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

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%

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

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 attempts

  1. 00:00 UTC

    Added to Previdian KEV Feed

    High-confidence, third-party report of exploitation attempts

  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.

Start 14-day Pro trial 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

Sample API response 
{
  "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 }
}