Vulnerability report

Exploited in the wild High confidence Not in CISA KEV

CVE-2025-34027

Versa Concerto Authentication Bypass File Write Remote Code Execution

Versa / Concerto · 12.1.2 to <= 12.2.0

Watch CVE-2025-34027 Browse KEV feed
Severity
CVSS 10.0 · Critical
Confidence
High
Exploit status
Exploited in the wild
EPSS
46.1%
First observed
—
Last observed
—

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2025-34027 is an unauthenticated Versa Concerto Authentication Bypass File Write Remote Code Execution. The Versa Concerto SD-WAN orchestration platform is vulnerable to an authentication bypass in the Traefik...

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?

Versa / Concerto 12.1.2 to <= 12.2.0.

What should we do?

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

Overview

Versa Concerto Authentication Bypass File Write Remote Code Execution

The Versa Concerto SD-WAN orchestration platform is vulnerable to an authentication bypass in the Traefik reverse proxy configuration, allowing at attacker to access administrative endpoints. The Spack upload endpoint can be leveraged for a Time-of-Check to Time-of-Use (TOCTOU) write in combination with a race condition to achieve remote code execution via path loading manipulation, allowing an unauthenticated actor to achieve remote code execution (RCE).This issue is known to affect Concerto from 12.1.2 through 12.2.0.

Additional versions may be vulnerable.

Versa Affected
Concerto
Through 12.2.0
Published
21 May 2025
Exploitation Reported
01 Aug 2025
Attack vector
Remote
Complexity
Low
Privileges
None
User interaction
None

Tags

nuclei_scanner

CVE References

  • CVE Record CVE.org · CVE Record https://www.cve.org/CVERecord?id=CVE-2025-34027
  • Exploit — projectdiscovery.io projectdiscovery.io · Exploit https://projectdiscovery.io/blog/versa-concerto-authentication-bypass...

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 01 Aug 2025

A trusted third party reported exploitation.

Proof of concept available

Nuclei Templates

Recorded 12 Jun 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.

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Source Added
The Shadowserver First 2025-08-01 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/2025/CVE-2025-34027.yaml 01 Jun 2026

Risk and context

Severity, weaknesses, and research context

CVSS v4.0

10.0 Critical

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

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

EPSS

46.1%

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

Weaknesses

Time-of-check Time-of-use (TOCTOU) Race Condition CWE-367

Potential Proof of Concepts

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

Versa Concerto API Path Based - Authentication Bypass

nuclei · Created Unknown

Timeline

From disclosure to observed exploitation

  1. 14:21 UTC

    Public PoC available

    Public proof-of-concept code published

  2. 15:34 UTC

    Nuclei template available

    Scanner coverage available

  3. 00:00 UTC

    Added to Previdian KEV Feed

    High-confidence, third-party attested exploitation

  4. 21:58 UTC

    CVE published

    Vulnerability disclosed publicly

  5. 19:15 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-2025-34027

Sample API response 
{
  "cve_id": "CVE-2025-34027",
  "confidence": "High",
  "cvss_score": 10.0,
  "cvss_estimated": false,
  "epss_score": 0.461,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": false
  },
  "sensor_telemetry": { "attempts": 0, "sensors": 0 }
}