CriticalCVE-2025-34027

Versa Concerto Authentication Bypass File Write Remote Code Execution (CVE-2025-34027)

Published 21.05.2025Last modified 25.08.2026Sources: CVE.org

Actively exploited
Source: VulnCheck KEV (opens in a new tab) How we classify
Public exploit

What is affected, what to do

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.

The vulnerability is being actively exploited; treat it as a priority. The available sources name no fixed version. Check the vendor guidance in the references below.

Affected: Versa Concerto lte 12.1.2..12.2.0

Not sure whether and how you are affected? Ask a question about this vulnerability

Metrics

10.0

Priority

XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

Source: Vendor (CNA), CVSS v4

9.0

CVSS v3

Severity Critical on the scale from 0 to 10.

Source: CVE.org

46.4 %

EPSS score

Elevated — model estimates 10-50% exploitation likelihood.

Source: FIRST EPSS, percentile 98.8

Show all metrics

Severity: Critical
Priority (0–325) The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first? Read in glossary: 137.15 Methodology
Exploit maturity An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack. Read in glossary: actively exploitedSource: VulnCheck KEV (opens in a new tab) How we classify
XIEM Effective CVSS XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command. Read in glossary: 10.0 Methodology
CVSS v3 CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions. Read in glossary: 9.0
CVSS v4 CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions. Read in glossary: 10.0
EPSS score The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“. Read in glossary: 46.4 %; Elevated — model estimates 10-50% exploitation likelihood.
EPSS percentile The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking. Read in glossary: 98.8; Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
KEV status The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching. Read in glossary: —
Published: 21.05.2025
CISA assessment (SSVC): Exploitation: none known · automatable · Technical impact: total; Source: CISA Vulnrichment, as of 28 May 2025
CWE CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect. Read in glossary: CWE-367

Detection rules

No NEOSEC detection rule is available for this vulnerability yet.

Classification under NIS2 and CRA

Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

NIS2 NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management. Read in glossary: Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
CRA The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates. Read in glossary: Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
ISO/IEC 27001 ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security. Read in glossary: Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

Description

Source: cvelistv5, NVD (NIST)

Affected products

The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

Affected products
		Affected versions	Fixed in
Versa	Concerto	`12.1.2 – ≤ 12.2.0`	—
versa-networks	concerto	`12.2.1` `12.1.2` `11.4.0 – ≤ 12.1.1`	— — —

Vendors and products

Weakness classes (CWE)

CWE-367Time-of-check Time-of-use (TOCTOU) Race Condition
Base
The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check.
Entry at MITRE CWE-367

Public exploit references

Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

Public exploit references

Reference tagged as exploit	projectdiscovery.io (opens in a new tab)	PoC (publicly reported)reported, not verified	—

References & sources

projectdiscovery.ioblog/versa-concerto-authentication-bypass-rceExploit, Mitigation

Changes to this CVE

Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

25.08.2026Reanalysis by NVDNVD

Product mapping changed:

Versa Concerto (11.4.0 – through 12.1.1; 2 individual versions)

Show the original change

Individual changes of this event as published by NVD
Type	Action	Before	After
Product configuration	changed	OR cpe:2.3:a:versa-networks:concerto:12.1.2:-::::::* cpe:2.3:a:versa-networks:concerto::::::::* versions up to (including) 12.1.1 cpe:2.3:a:versa-networks:concerto:12.2.1:-::::::*	OR cpe:2.3:a:versa-networks:concerto:12.1.2:-::::::* cpe:2.3:a:versa-networks:concerto:12.2.1:-::::::* cpe:2.3:a:versa-networks:concerto::::::::* versions from (including) 11.4.0 up to (including) 12.1.1

Source identifier: nvd@nist.gov

25.08.2026Initial analysis by NVDNVD

Newly listed as affected:

Versa Concerto (through 12.1.1; 2 individual versions)

CVSS V3.1: AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H

New references:

https://projectdiscovery.io/blog/versa-concerto-authentication-bypass-rce

Show 4 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
CVSS	added	—	AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
Product configuration	added	—	OR cpe:2.3:a:versa-networks:concerto:12.1.2:-::::::* cpe:2.3:a:versa-networks:concerto::::::::* versions up to (including) 12.1.1 cpe:2.3:a:versa-networks:concerto:12.2.1:-::::::*
Reference type	added	—	VulnCheck: https://projectdiscovery.io/blog/versa-concerto-authentication-bypass-rce Types: Exploit, Third Party Advisory
Reference type	added	—	CISA-ADP: https://projectdiscovery.io/blog/versa-concerto-authentication-bypass-rce Types: Exploit, Third Party Advisory

Source identifier: nvd@nist.gov

Embed badge

Show the severity and KEV status of this vulnerability on your site – with a link back here. The image is updated hourly.

<a href="https://intel.neosec.eu/en/cve/CVE-2025-34027"><img src="https://intel.neosec.eu/badge/cve/CVE-2025-34027.svg?lang=en" alt="CVE-2025-34027 – NEOSEC Intel" height="20"></a>