Security readout for executives and security teams
Plain-English summary
An authenticated Flowise user may gain control of the server by abusing the Custom MCP node when it uses the stdio protocol. Successful exploitation could expose data, alter workflows, disrupt service, and affect connected systems. The issue is rated critical, but the supplied sources do not report active exploitation.
Executive priority
Treat this as an immediate remediation item for any qualifying deployment. Prioritize externally reachable and multi-user Flowise systems, restrict access while upgrading, and investigate suspicious Custom MCP activity. Systems without stdio-based Custom MCP are lower priority but should still have their versions verified.
Technical view
Flowise before 3.1.3 allows command execution through insufficient validation of Custom MCP environment variables and command arguments when CUSTOM_MCP_PROTOCOL is stdio. The CVSS 4.0 score is 9.0, with network access, low privileges, and no user interaction required, although an additional attack condition is present.
Likely exposure
Exposure requires Flowise before 3.1.3, an authenticated account, and Custom MCP operating through stdio. Internet-accessible or broadly shared deployments are especially concerning because low-privileged users may reach server-level execution. The bundle's structured affected-version entries are internally inconsistent, so confirm scope against the vendor advisory.
Exploitation context
The supplied record is not in CISA KEV and provides no evidence of active exploitation. Public advisories describe specific command-validation bypasses, demonstrating technical plausibility, but the prevalence of vulnerable configurations and real-world attacks remains unknown.
Researcher notes
CWE-95 and the advisory description indicate attacker-controlled input reaches command execution paths. Preconditions are authenticated access and stdio protocol use. The bundled affected array lists versions ambiguously while marking default status unaffected; therefore, use the explicit “before 3.1.3” advisory scope and verify it with FlowiseAI.
Mitigation direction
- Upgrade Flowise to version 3.1.3 or later after reviewing the vendor advisory.
- Disable or restrict Custom MCP stdio operation until upgrading is complete.
- Limit Flowise accounts and Custom MCP access to trusted administrators.
- Review vendor guidance for any additional configuration-specific remediation.
Validation and detection
- Inventory every Flowise deployment and record its exact installed version.
- Determine whether CUSTOM_MCP_PROTOCOL is configured as stdio.
- Identify users authorized to create, edit, or execute Custom MCP nodes.
- Review Custom MCP configurations and logs for unexpected environment variables or command arguments.
- Confirm the upgraded service reports version 3.1.3 or later.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-95: Code execution behavior lookup
Code execution and unsafe deserialization weaknesses often justify reviewing execution behavior and process telemetry. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2026-73601 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Critical
- CVSS
- 9 (4.0)
- Known Exploited
- No
- Published
Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
SSVC decision data
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H——VulnCheckVulnerability scoring details
Base CVSS 4.0 score
9CriticalVector: CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- GitHub Security Advisory (GHSA-g98q-rm45-q9h8)CVE reference, VulnCheck · vendor-advisory
- VulnCheck Advisory: Flowise before 3.1.3 Remote Code Execution via Custom MCPCVE reference, VulnCheck · third-party-advisory
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Neutralization of Directives in Dynamically Evaluated Code ('Eval Injection')
Improper Neutralization of Directives in Dynamically Evaluated Code ('Eval Injection') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.