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CVE-2026-8467 is a low severity vulnerability with a CVSS score of 0.0. No known exploits currently, and patches are available.
Lower probability of exploitation
EPSS predicts the probability of exploitation in the next 30 days based on real-world threat data, complementing CVSS severity scores with actual risk assessment.
An unsafe HEEx template generation vulnerability allows any unauthenticated user to execute arbitrary code on the server. The phoenix_storybook playground accepts user-controlled attribute values over WebSocket and interpolates them unsanitized into a HEEx template that is subsequently compiled and evaluated with full Elixir Kernel access.
The vulnerability is a three-step chain:
1. Unsanitized WebSocket input (extra_assigns_helpers.ex)
The psb-assign event handler in PhoenixStorybook.Story.PlaygroundPreviewLive accepts arbitrary attribute names and values from unauthenticated WebSocket clients and stores them verbatim via ExtraAssignsHelpers.handle_set_variation_assign/3.
2. Unescaped interpolation into HEEx (component_renderer.ex)
ComponentRenderer.attributes_markup/1 builds a HEEx template string by interpolating binary attribute values directly:
{name, val} when is_binary(val) ->
~s|#{name}="#{val}"|
No escaping of " or { is performed. A value such as foo" injected={EXPR} bar=" breaks out of the attribute string and injects EXPR as an inline HEEx expression.
3. Unsandboxed evaluation (component_renderer.ex)
The resulting HEEx string is compiled via EEx.compile_string/2 and evaluated via Code.eval_quoted_with_env/3 with full Kernel imports and no sandbox. The injected expression executes on the server even if it causes a rendering error.
/storybook/core_components/button).psb-assign event with an attribute value that escapes the HEEx attribute context and embeds an Elixir expression (e.g. a System.cmd/2 call).Please cite this page when referencing data from Strobes VI. Proper attribution helps support our vulnerability intelligence research.
No authentication, no special configuration, and no user interaction are required.
This is a pre-authentication remote code execution vulnerability. Any user able to reach the storybook endpoint, including unauthenticated internet users if the storybook is publicly deployed, can execute arbitrary operating system commands with the privileges of the server process. All versions of phoenix_storybook from 0.5.0 before 1.1.0 are affected.