CVE-2026-76804 in Nuclei
Summary
by MITRE • 09/22/2026
Nuclei is a vulnerability scanner built on a simple YAML-based DSL. From 3.0.0 until 3.10.0, the workflow template loading path does not enforce the -file capability gate when resolving file: protocol templates referenced by a workflow. An untrusted unsigned workflow can therefore load a file-protocol template and read local files from the scanner host even when the operator has not enabled file templates. The issue affects CLI users running workflows with -w and SDK integrations that accept end-user workflows while relying on the default file-access restriction. This issue is fixed in version 3.10.0.
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Analysis
by VulDB Data Team • 09/22/2026
The vulnerability identified within Nuclei versions ranging from 3.0.0 to 3.10.0 represents a critical failure in access control mechanisms regarding template loading protocols. Nuclea operates as a powerful vulnerability scanner driven by YAML-based domain-specific language templates, allowing security professionals and automated systems to define complex scanning workflows. A core security feature of this tool is the ability to restrict file system access via specific command-line flags or configuration gates, such as the -file capability gate. This mechanism is designed to prevent scanners from reading arbitrary local files on the host machine, thereby mitigating risks associated with information disclosure and path traversal attacks when processing untrusted inputs. However, a logic flaw exists in how workflow templates resolve references to file-protocol templates. Specifically, when a workflow template loads another template using the file: protocol, the system fails to enforce the previously established -file capability gate. This oversight means that even if an operator has explicitly disabled or not enabled file-based template loading for direct execution, indirect access through a workflow structure bypasses this restriction entirely.
This architectural flaw allows an untrusted and unsigned workflow to act as a vector for reading local files from the scanner host machine. In practical terms, an attacker who can supply a malicious workflow template to Nuclei can craft it to reference internal system files via the file: protocol. Because the validation logic does not check whether the parent context permits file access, the scanner proceeds to load and process these templates without raising an error or blocking the operation. This effectively neutralizes the intended security boundary that protects against local information disclosure. The impact is particularly severe for CLI users who execute workflows using the -w flag and for SDK integrations that accept end-user provided workflows while relying on default file-access restrictions. In both scenarios, the assumption that disabling direct file template loading also prevents indirect access through workflow chains proves incorrect due to this implementation gap.
From a classification perspective, this vulnerability aligns with CWE-284 Improper Access Control and CWE-732 Incorrect Permission Assignment for Critical Resource. The failure lies in the inconsistent enforcement of security policies across different code paths within the application logic. Furthermore, from an offensive security standpoint as mapped by MITRE ATT&CK, this behavior facilitates Local File Inclusion (LFI) techniques often categorized under T1083 or related data exfiltration tactics where attackers leverage trusted applications to read sensitive local resources. The ability to bypass intended access controls through indirect invocation is a classic example of logic-based vulnerabilities that are difficult to detect via static analysis alone because the code technically performs file reading, but only in an unauthorized context according to policy definitions.
The operational impact extends beyond simple data leakage. By accessing arbitrary files on the host system, an attacker could potentially retrieve configuration files containing credentials, private keys, or other sensitive metadata stored locally. This information can then be used for further exploitation within the target environment or exfiltrated externally if combined with network-based capabilities of the scanner. For organizations integrating Nuclei into their CI/CD pipelines or automated security testing frameworks via SDKs, this vulnerability poses a significant risk if they process templates from untrusted sources without rigorous validation and sandboxing measures beyond what the tool provides by default. The trust model assumes that workflow inputs are safe unless explicitly allowed to access files, but the flaw breaks this assumption for indirect file accesses initiated through workflows.
To mitigate this issue, users must upgrade Nuclei to version 3.10.0 or later where the logic has been corrected to properly enforce the -file capability gate regardless of whether the template is loaded directly or indirectly via a workflow. Until an update can be applied, operators should strictly avoid using workflows sourced from untrusted parties and ensure that no sensitive data resides in locations accessible by standard file protocols if such workflows must be processed. Additionally, implementing strict input validation at the integration layer for SDK users is advisable to filter out any template references attempting to use the file: protocol unless explicitly authorized through secure configuration channels. This incident highlights the importance of comprehensive security testing that covers not just direct API calls but also complex interaction patterns like workflow chaining in vulnerability scanning tools.