Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain
-
ReconNetwork scan identifies SINEC NMS instance
-
DeliveryCraft malicious JWT bypassing signature validation
-
ExploitSubmit token to UMC authentication endpoint
-
InstallGain unauthorized authenticated session
-
C2Access network management functions
-
ExecuteEnumerate OT infrastructure topology
-
ImpactExfiltrate credentials or modify configurations
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A04:2025 - Cryptographic Failures
ASVS 5.0
V11 - Cryptography Signature verification
|
| Impact | Real-world risk is HIGH despite moderate CVSS 7.3 score. The CVSS vector reveals optimal attacker conditions: network-accessible (AV:N), low attack complexity (AC:L), no privileges required (PR:N), and no user interaction needed (UI:N). While impact ratings are partial (C:L/I:L/A:L), authentication bypass in industrial network management systems provides attackers a foothold for lateral movement, reconnaissance of OT infrastructure, and potential manipulation of network configurations. EPSS data not provided, but similar authentication bypass vulnerabilities in ICS/SCADA contexts historically show elevated exploitation interest. No CISA KEV listing indicates no confirmed active exploitation campaigns at present. The JWT-specific nature (per tags) means exploit development is straightforward for experienced attackers familiar with common JWT vulnerabilities. Priority should be elevated for organizations running SINEC NMS in production OT environments, particularly those with internet-exposed or cross-network accessible management interfaces. The SSVC framework would likely classify this as high technical impact with automatable exploitation given the authentication bypass nature. |
| Exploit ScenarioDerived | An unauthenticated remote attacker identifies a SINEC NMS V3.x installation accessible via corporate network or internet exposure. The attacker crafts malicious JWT tokens exploiting signature validation weaknesses in the UMC component, such as submitting unsigned tokens or manipulating the algorithm header to bypass cryptographic verification. Upon successful authentication bypass, the attacker gains unauthorized access to the SINEC NMS interface with legitimate user privileges, enabling reconnaissance of managed industrial network topology, extraction of device configurations and credentials, manipulation of network policies, or establishment of persistent access for subsequent operational technology environment compromise. |
Get an e-mail when this CVE is exploited, patched or re-scored. Free account.
Alert meAnalysisAIv1 – Apr 14, 2026
Authentication bypass in Siemens SINEC NMS versions prior to V4.0 SP3 with UMC allows unauthenticated remote attackers to gain unauthorized access due to insufficient user identity validation in the UMC component (CWE-347: Improper Verification of Cryptographic Signature). The vulnerability enables network-based attacks with low complexity requiring no user interaction (CVSS 7.3, AV:N/AC:L/PR:N/UI:N), granting partial access to confidentiality, integrity, and availability. ZDI tracking ID CAN-27564 suggests coordinated disclosure. No active exploitation (CISA KEV) or public exploit code confirmed at time of analysis, though JWT-related authentication bypasses are well-understood attack primitives.
RemediationAI
Upgrade to Siemens SINEC NMS V4.0 SP3 or later, which addresses the authentication bypass vulnerability in the UMC component. Siemens ProductCERT advisory SSA-801704 available at https://cert-portal.siemens.com/productcert/html/ssa-801704.html provides official patch guidance and installation instructions. As interim mitigation measures until patching is feasible, restrict network access to SINEC NMS management interfaces using firewall rules limiting connectivity to trusted administrative networks only, disable UMC component if not operationally required, implement network segmentation isolating the management system from untrusted networks, and enable comprehensive logging to detect potential unauthorized access attempts. Organizations should prioritize patching for internet-facing or cross-zone accessible SINEC NMS deployments given the unauthenticated remote attack vector.
Affected VersionsENISA
Affects your stack
Find out whether the stacks and servers you run are on an affected version.
Checking this CVE against your own stacks and servers is part of the Basic plan and up.
Technical ContextAI · show details
The vulnerability resides in the User Management Console (UMC) component of Siemens SINEC Network Management System, an industrial network management platform. CWE-347 indicates improper verification of cryptographic signatures, commonly associated with JSON Web Token (JWT) implementation flaws. Typical JWT authentication bypass scenarios include algorithm confusion attacks (switching RS256 to HS256), signature stripping (accepting unsigned tokens), weak secret keys, or acceptance of self-signed tokens without proper validation. The SINEC NMS platform manages industrial Ethernet networks in operational technology environments, making authentication failures particularly critical as they expose network configuration, device management, and monitoring capabilities to unauthorized actors. The CPE identifier cpe:2.3:a:siemens:sinec_nms confirms all versions prior to the patched release are affected.
Know when Sinec Nms gets its next vulnerability
- Watch products and get an email when something new is published
- Check this CVE against your own stack and servers
- Exploit and PoC references, threat intelligence from 22 sources
No credit card · 7-day full trial
Severity by source
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N
Primary rating from Vendor (siemens) · only source for this CVE.
CVSS VectorVendor: siemens
Lifecycle Timeline
3DescriptionCVE.org
A vulnerability has been identified in SINEC NMS (All versions < V4.0 SP3 with UMC). The affected application contains an authentication weakness due to insufficient validation of user identity in the UMC component. This could allow an unauthenticated remote attacker to bypass authentication and gain unauthorized access to the application. (ZDI-CAN-27564)
Zero Day Initiative Advisories
Executive ViewAI
Siemens SINEC NMS versions prior to V4.0 SP3 contain an authentication bypass vulnerability in the UMC component that allows unauthenticated remote attackers to gain unauthorized access to the network management system. This vulnerability directly impacts the confidentiality, integrity, and availability of critical infrastructure network management capabilities and requires immediate inventory and containment actions across all affected deployments.
No vendor-released patch identified at time of analysis. Interim mitigations: (1) Restrict SINEC NMS network access via firewall rules to authorized management IP ranges only; (2) Disable UMC component if operationally feasible; (3) Implement web application firewall (WAF) rules to detect and block suspicious authentication token manipulation; (4) Enable comprehensive logging and SIEM alerting on UMC authentication failures and token validation errors; (5) Conduct immediate access review of SINEC NMS systems to identify and revoke unauthorized credentials. Monitor Siemens security advisories weekly for patch availability.
Threat Intelligence Overview
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.
A crafted request uri-path can cause mod_proxy to forward the request to an origin server choosen by the remote user.4.4
An OpenSSL TLS server may crash if sent a maliciously crafted renegotiation ClientHello message from a client. Rated med
SINEC NMS versions prior to V4.0 SP3 allow authenticated remote attackers to reset any user account password due to impr
In logback version 1.2.7 and prior versions, an attacker with the required privileges to edit configurations files could
A vulnerability has been identified in SINEC NMS (All versions < V4.0). The affected application exposes an endpoint tha
A vulnerability has been identified in SINEC NMS (All versions < V2.0 SP1). Rated critical severity (CVSS 9.8), this vul
ap_escape_quotes() may write beyond the end of a buffer when given malicious input. Rated critical severity (CVSS 9.8),
A vulnerability has been identified in SINEC NMS (All versions < V3.0). Rated critical severity (CVSS 9.4), this vulnera
A vulnerability has been identified in SINEC NMS (All versions < V1.0 SP2 Update 1). Rated critical severity (CVSS 9.1),
A vulnerability has been identified in SINEC NMS (All versions < V1.0 SP2 Update 1). Rated critical severity (CVSS 9.1),
A vulnerability has been identified in SINEC NMS (All versions < V4.0). The affected application does not properly valid
A vulnerability has been identified in SINEC NMS (All versions < V4.0). The affected application does not properly valid
EUVD-2026-22233
GHSA-7f3f-wq83-6q76
NVD
CVE.org
EPSS
Vulnrichment
Exploit-DB