CVE-2026-118649 in n8n
Summary
by MITRE • 10/28/2026
n8n before 2.43.5 and 2.44.x before 2.44.1 accepts a client-supplied workflow ID and caches each workflow's owner project in memory by that ID, so a crafted ID such as __proto__ makes the Data Table project check match every project. An authenticated member who can create and run workflows can list, read, modify, and delete Data Table rows in all projects of the instance.
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Analysis
by VulDB Data Team • 10/28/2026
The vulnerability identified in n8n versions prior to 2.43.5 and version 2.44.x prior to 2.44.1 represents a critical security flaw rooted in improper handling of user-supplied input within an internal caching mechanism. The core technical issue arises from the application's practice of storing workflow owner project identifiers in memory using the client-provided workflow ID as the primary key for lookup operations. This design choice inadvertently exposes the system to prototype pollution attacks, specifically targeting JavaScript object prototypes when the underlying data structure is implemented as a standard associative array or plain object without proper isolation mechanisms such as Map objects with null-prototype keys or strict input validation.
By supplying a specially crafted workflow ID containing the string _proto_, an attacker can manipulate the internal caching logic to overwrite properties on the Object prototype chain rather than storing data in the intended instance-specific cache slot. This manipulation causes subsequent checks against Data Table projects to match every project within the n8n instance, effectively bypassing access control boundaries that are normally enforced based on project ownership or user permissions. The flaw exploits the fundamental behavior of JavaScript objects where setting properties on _proto_ affects all object instances derived from it, leading to a complete breakdown of logical isolation between distinct tenant projects in multi-tenant deployments.
The operational impact of this vulnerability is severe for authenticated users who possess the ability to create and execute workflows within the n8n environment. Once the prototype pollution is achieved, these authorized but potentially malicious actors gain unrestricted access to Data Table resources across all projects hosted on the instance. This includes the capability to list existing data entries, read sensitive information stored in tables, modify critical records, and delete essential data rows without restriction. The scope of this impact extends beyond individual project boundaries, compromising the integrity and confidentiality of the entire multi-tenant environment by allowing lateral movement between isolated workspaces that should remain strictly segregated.
From a classification perspective, this vulnerability aligns with CWE-1321: Prototype Pollution in JavaScript, which describes flaws where an attacker can modify properties on Object.prototype due to improper validation or merging of user-controlled objects into existing structures. Additionally, the exploitation technique maps directly to MITRE ATT&CK tactic Tactic TA0005: Defense Evasion and specifically Technique T1623: Impersonation with _proto_, which details how attackers use prototype manipulation to bypass security controls and escalate privileges within an application context. The vulnerability also reflects CWE-862: Missing Authorization, as the access control checks fail to verify that the requesting user actually owns or has permission to access the targeted project resources due to the corrupted state of the internal lookup mechanism.
Mitigation strategies must prioritize immediate upgrading to n8n version 2.43.5 or later for stable releases and version 2.44.1 or later for development branches, as these versions contain patches that address the prototype pollution vector by implementing safer data structures such as Map objects with null prototypes or enforcing strict input sanitization on workflow IDs before they are used as cache keys. For environments where immediate patching is not feasible, administrators should enforce rigorous input validation to reject any workflow identifiers containing special characters like underscores followed by proto strings and restrict the creation of workflows for users who do not require elevated privileges. Furthermore, implementing Web Application Firewall rules that detect attempts to inject prototype manipulation payloads into API endpoints can provide an additional layer of defense against exploitation while long-term architectural improvements are pursued to ensure all internal caches utilize secure data structures resistant to JavaScript-specific injection attacks.