Nuclei EUVD-2026-84554

Requires the operator/victim to load and execute an untrusted, unsigned Nuclei workflow via the CLI -w flag, or an SDK integration that accepts end-user-supplied workflows while relying on the default file-access restriction. Crucially, the -file capability flag (EnableFileTemplates) does NOT need to be enabled - the bypass is precisely that the workflow loading path fails to enforce this gate for file:-protocol templates referenced by a workflow. Limiting factors: exploitation is local (attacker cannot trigger remotely without the operator running their workflow - UI:R), affects only Nuclei versions 3.0.0 through 3.9.x, and yields only file read (no code execution or modification). Signed/verified workflows and single-template runs that respect the gate are not the vulnerable path.

This is a moderate-severity, confidentiality-only issue whose real-world risk is well-captured by the vendor's 5.5 CVSS score. The vector CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N is coherent with the description: exploitation is LOCAL (AV:L) and requires the operator to actually load and run an attacker-supplied workflow (UI:R), which is the dominant limiting factor. No privileges are needed (PR:N) because the attacker supplies content, not credentials. Impact is high confidentiality (arbitrary local file read from the scanner host) with no integrity or availability effect. No EPSS score, no CISA KEV entry, and no public exploit code were provided in the intelligence, so there is no public exploit identified at time of analysis and no evidence of active exploitation - this is a latent access-control weakness, not an urgent in-the-wild threat. It is a real but modest priority: patch during normal cadence, prioritized higher for teams that run community/third-party Nuclei workflows or expose Nuclei-as-a-service via the SDK. Note the tag mislabeling: 'Authentication Bypass' is inaccurate - this is a capability/authorization-gate bypass (CWE-284), not an auth bypass. There are no conflicting signals between the CVSS vector and the description; both consistently indicate local, user-interaction-gated file disclosure.

An attacker publishes a seemingly-benign Nuclei workflow (or submits one to an SDK-based scanning service) that references a file:-protocol template. When a victim runs it with nuclei -w evil-workflow.yaml - without ever enabling -file - the workflow loader resolves the file template and reads sensitive local files (e.g. SSH keys, cloud credentials, config) from the scanner host, exfiltrating them via the template's output. No public exploit code is identified, but the technique is straightforward given the well-documented file: protocol and the low attack complexity (AC:L).