{"id":"CVE-2026-8467","aliases":["EEF-CVE-2026-8467","EUVD-2026-31112","GHSA-55hg-8qxv-qj4p"],"status":"published","title":"Unauthenticated remote code execution via HEEx template injection in phoenix_storybook playground","description":"Code Injection vulnerability in phenixdigital phoenix_storybook allows unauthenticated remote code execution via unsanitized attribute value interpolation in HEEx template generation.\n\nThe psb-assign WebSocket event handler in 'Elixir.PhoenixStorybook.Story.PlaygroundPreviewLive':handle_event/3 accepts arbitrary attribute names and values from unauthenticated clients. These values are passed to 'Elixir.PhoenixStorybook.Helpers.ExtraAssignsHelpers':handle_set_variation_assign/3, which stores them verbatim. When rendering, 'Elixir.PhoenixStorybook.Rendering.ComponentRenderer':attributes_markup/1 interpolates binary attribute values directly into a HEEx template string as name=\"\u003cval\u003e\" without escaping double quotes or HEEx expression delimiters. An attacker can supply a value containing a closing quote followed by a HEEx expression block (e.g. foo\" injected={EXPR} bar=\"), which causes EXPR to be treated as an inline Elixir expression. The resulting template is compiled via EEx.compile_string/2 and executed via Code.eval_quoted_with_env/3 with full Kernel imports and no sandbox, giving the attacker arbitrary code execution on the server.\n\nThis issue affects phoenix_storybook from 0.5.0 before 1.1.0.","severity":{"version":"4.0","score":9.5,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H","level":"critical","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-09","score":0.02111,"percentile":0.81931,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":true,"fix_available":true},"cwes":["CWE-94"],"published":"2026-05-20T13:35:29Z","modified":"2026-10-28T02:30:44Z","exploits":[{"source":"pocgithub","id":"HORKimhab/CVE-2026-8467","title":"HORKimhab/CVE-2026-8467","date":"2026-08-27","url":"https://github.com/HORKimhab/CVE-2026-8467"}],"fixes":[{"ecosystem":"Hex","package":"phoenix_storybook","fixed_in":["1.1.0"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"Hex","package":"phoenix_storybook","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0.5.0"},{"fixed":"1.1.0"}]}]},{"source":"osv","ecosystem":"Hex","package":"phoenix_storybook","ranges":[{"type":"SEMVER","events":[{"introduced":"0.5.0"},{"fixed":"1.1.0"}]}],"versions":["0.5.0","0.5.1","0.5.2","0.5.3","0.5.4","0.5.5","0.5.6","0.5.7","0.6.0","0.6.1","0.6.2","0.6.3","0.6.4","0.7.0","0.7.1","0.7.2","0.8.0","0.8.1","0.8.2","0.8.3","0.9.0","0.9.1","0.9.2","0.9.3","1.0.0"]},{"source":"osv","ecosystem":"Hex","package":"phoenix_storybook","ranges":[{"type":"SEMVER","events":[{"introduced":"0.5.0"},{"fixed":"1.1.0"}]}],"versions":["0.5.0","0.5.1","0.5.2","0.5.3","0.5.4","0.5.5","0.5.6","0.5.7","0.6.0","0.6.1","0.6.2","0.6.3","0.6.4","0.7.0","0.7.1","0.7.2","0.8.0","0.8.1","0.8.2","0.8.3","0.9.0","0.9.1","0.9.2","0.9.3","1.0.0"]}],"products":[{"vendor":"phenixdigital","product":"phoenix_storybook"}],"references":[{"url":"https://github.com/phenixdigital/phoenix_storybook/security/advisories/GHSA-55hg-8qxv-qj4p","tags":["vendor-advisory","related","exploit","advisory","web"]},{"url":"https://cna.erlef.org/cves/CVE-2026-8467.html","tags":["related","web"]},{"url":"https://osv.dev/vulnerability/EEF-CVE-2026-8467","tags":["related","web"]},{"url":"https://github.com/phenixdigital/phoenix_storybook/commit/56ab8464d4375fa52db806148a06cce126ad481d","tags":["patch","fix","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-8467","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-55hg-8qxv-qj4p"},{"url":"https://github.com","tags":["web"]},{"url":"https://repo.hex.pm","tags":["web"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/8xxx/CVE-2026-8467.json","tags":["advisory"]},{"url":"https://github.com/phenixdigital/phoenix_storybook","tags":["package"]},{"url":"https://hex.pm/packages/phoenix_storybook","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-8467","title":"Unauthenticated remote code execution via HEEx template injection in phoenix_storybook playground","description":"Code Injection vulnerability in phenixdigital phoenix_storybook allows unauthenticated remote code execution via unsanitized attribute value interpolation in HEEx template generation.\n\nThe psb-assign WebSocket event handler in 'Elixir.PhoenixStorybook.Story.PlaygroundPreviewLive':handle_event/3 accepts arbitrary attribute names and values from unauthenticated clients. These values are passed to 'Elixir.PhoenixStorybook.Helpers.ExtraAssignsHelpers':handle_set_variation_assign/3, which stores them verbatim. When rendering, 'Elixir.PhoenixStorybook.Rendering.ComponentRenderer':attributes_markup/1 interpolates binary attribute values directly into a HEEx template string as name=\"\u003cval\u003e\" without escaping double quotes or HEEx expression delimiters. An attacker can supply a value containing a closing quote followed by a HEEx expression block (e.g. foo\" injected={EXPR} bar=\"), which causes EXPR to be treated as an inline Elixir expression. The resulting template is compiled via EEx.compile_string/2 and executed via Code.eval_quoted_with_env/3 with full Kernel imports and no sandbox, giving the attacker arbitrary code execution on the server.\n\nThis issue affects phoenix_storybook from 0.5.0 before 1.1.0.","status":"published","published":"2026-05-20T13:35:29.018Z","modified":"2026-05-27T15:41:02.357Z","cvss":[{"version":"4.0","score":9.5,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H","level":"critical","assessor":"cna"}],"cwes":["CWE-94"],"updated_at":"2026-11-02T13:48:13.398044Z"}],"euvd":[{"id":"EUVD-2026-31112","description":"Code Injection vulnerability in phenixdigital phoenix_storybook allows unauthenticated remote code execution via unsanitized attribute value interpolation in HEEx template generation.\n\nThe psb-assign WebSocket event handler in 'Elixir.PhoenixStorybook.Story.PlaygroundPreviewLive':handle_event/3 accepts arbitrary attribute names and values from unauthenticated clients. These values are passed to 'Elixir.PhoenixStorybook.Helpers.ExtraAssignsHelpers':handle_set_variation_assign/3, which stores them verbatim. When rendering, 'Elixir.PhoenixStorybook.Rendering.ComponentRenderer':attributes_markup/1 interpolates binary attribute values directly into a HEEx template string as name=\"\u003cval\u003e\" without escaping double quotes or HEEx expression delimiters. An attacker can supply a value containing a closing quote followed by a HEEx expression block (e.g. foo\" injected={EXPR} bar=\"), which causes EXPR to be treated as an inline Elixir expression. The resulting template is compiled via EEx.compile_string/2 and executed via Code.eval_quoted_with_env/3 with full Kernel imports and no sandbox, giving the attacker arbitrary code execution on the server.\n\nThis issue affects phoenix_storybook from 0.5.0 before 1.1.0.","status":"published","published":"2026-05-20T13:35:29Z","modified":"2026-05-27T15:41:02Z","cvss":[{"version":"4.0","score":9.5,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H","level":"critical"}],"updated_at":"2026-11-02T18:21:03.926243Z"}],"ghsa":[{"id":"GHSA-55hg-8qxv-qj4p","title":"PhoenixStorybook: Unauthenticated remote code execution via HEEx template injection in phoenix_storybook playground","description":"### Summary\nAn 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.\n\n### Details\nThe vulnerability is a three-step chain:\n\n**1. Unsanitized WebSocket input (`extra_assigns_helpers.ex`)**\nThe `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`.\n\n**2. Unescaped interpolation into HEEx (`component_renderer.ex`)**\n`ComponentRenderer.attributes_markup/1` builds a HEEx template string by interpolating binary attribute values directly:\n```elixir\n{name, val} when is_binary(val) -\u003e\n  ~s|#{name}=\"#{val}\"|\n```\nNo 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.\n\n**3. Unsandboxed evaluation (`component_renderer.ex`)**\nThe 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.\n\n### PoC\n1. Identify any story URL with a Playground tab (e.g. `/storybook/core_components/button`).\n2. Connect to the Phoenix LiveView WebSocket without any authentication.\n3. Join the story's LiveView channel and send a `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).\n4. The server evaluates the injected expression and returns its output in the rendered response.\n\nNo authentication, no special configuration, and no user interaction are required.\n\n### Impact\nThis 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.\n\n## Resources\n\n* Introduction Commit: https://github.com/phenixdigital/phoenix_storybook/commit/e35379dfe2ef1a71b141899e36f431017c55265d\n* Patch Commit: https://github.com/phenixdigital/phoenix_storybook/commit/56ab8464d4375fa52db806148a06cce126ad481d","status":"published","published":"2026-06-09T21:58:57Z","modified":"2026-06-09T21:58:58Z","cvss":[{"version":"4.0","score":9.5,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H","level":"critical"}],"cwes":["CWE-94"],"updated_at":"2026-11-02T14:40:24.856614Z"}],"nvd":[{"id":"CVE-2026-8467","description":"Code Injection vulnerability in phenixdigital phoenix_storybook allows unauthenticated remote code execution via unsanitized attribute value interpolation in HEEx template generation.\n\nThe psb-assign WebSocket event handler in 'Elixir.PhoenixStorybook.Story.PlaygroundPreviewLive':handle_event/3 accepts arbitrary attribute names and values from unauthenticated clients. These values are passed to 'Elixir.PhoenixStorybook.Helpers.ExtraAssignsHelpers':handle_set_variation_assign/3, which stores them verbatim. When rendering, 'Elixir.PhoenixStorybook.Rendering.ComponentRenderer':attributes_markup/1 interpolates binary attribute values directly into a HEEx template string as name=\"\u003cval\u003e\" without escaping double quotes or HEEx expression delimiters. An attacker can supply a value containing a closing quote followed by a HEEx expression block (e.g. foo\" injected={EXPR} bar=\"), which causes EXPR to be treated as an inline Elixir expression. The resulting template is compiled via EEx.compile_string/2 and executed via Code.eval_quoted_with_env/3 with full Kernel imports and no sandbox, giving the attacker arbitrary code execution on the server.\n\nThis issue affects phoenix_storybook from 0.5.0 before 1.1.0.","status":"published","published":"2026-05-20T14:17:04.283Z","modified":"2026-07-23T12:10:00.11Z","cvss":[{"version":"4.0","score":9.5,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"critical","assessor":"secondary"}],"cwes":["CWE-94"],"updated_at":"2026-11-02T14:12:19.752984Z"}],"osv":[{"id":"CVE-2026-8467","title":"Unauthenticated remote code execution via HEEx template injection in phoenix_storybook playground","description":"Code Injection vulnerability in phenixdigital phoenix_storybook allows unauthenticated remote code execution via unsanitized attribute value interpolation in HEEx template generation.\n\nThe psb-assign WebSocket event handler in 'Elixir.PhoenixStorybook.Story.PlaygroundPreviewLive':handle_event/3 accepts arbitrary attribute names and values from unauthenticated clients. These values are passed to 'Elixir.PhoenixStorybook.Helpers.ExtraAssignsHelpers':handle_set_variation_assign/3, which stores them verbatim. When rendering, 'Elixir.PhoenixStorybook.Rendering.ComponentRenderer':attributes_markup/1 interpolates binary attribute values directly into a HEEx template string as name=\"\u003cval\u003e\" without escaping double quotes or HEEx expression delimiters. An attacker can supply a value containing a closing quote followed by a HEEx expression block (e.g. foo\" injected={EXPR} bar=\"), which causes EXPR to be treated as an inline Elixir expression. The resulting template is compiled via EEx.compile_string/2 and executed via Code.eval_quoted_with_env/3 with full Kernel imports and no sandbox, giving the attacker arbitrary code execution on the server.\n\nThis issue affects phoenix_storybook from 0.5.0 before 1.1.0.","status":"published","published":"2026-05-20T13:35:29.018Z","modified":"2026-10-28T02:30:44.008391055Z","cvss":[{"version":"4.0","score":9.5,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H","level":"critical"}],"cwes":["CWE-94"],"updated_at":"2026-11-02T15:45:18.482949Z"},{"id":"EEF-CVE-2026-8467","title":"Unauthenticated remote code execution via HEEx template injection in phoenix_storybook playground","description":"## Summary\n\nCode Injection vulnerability in phenixdigital phoenix\\_storybook allows unauthenticated remote code execution via unsanitized attribute value interpolation in HEEx template generation.\n\nThe psb-assign WebSocket event handler in 'Elixir.PhoenixStorybook.Story.PlaygroundPreviewLive':handle\\_event/3 accepts arbitrary attribute names and values from unauthenticated clients. These values are passed to 'Elixir.PhoenixStorybook.Helpers.ExtraAssignsHelpers':handle\\_set\\_variation\\_assign/3, which stores them verbatim. When rendering, 'Elixir.PhoenixStorybook.Rendering.ComponentRenderer':attributes\\_markup/1 interpolates binary attribute values directly into a HEEx template string as name=\"\u003cval\u003e\" without escaping double quotes or HEEx expression delimiters. An attacker can supply a value containing a closing quote followed by a HEEx expression block (e.g. foo\" injected={EXPR} bar=\"), which causes EXPR to be treated as an inline Elixir expression. The resulting template is compiled via EEx.compile\\_string/2 and executed via Code.eval\\_quoted\\_with\\_env/3 with full Kernel imports and no sandbox, giving the attacker arbitrary code execution on the server.\n\nThis issue affects phoenix\\_storybook from 0.5.0 before 1.1.0.","status":"published","published":"2026-05-20T13:35:29.018Z","modified":"2026-07-30T18:22:11.743435Z","cvss":[{"version":"4.0","score":9.5,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H","level":"critical"}],"cwes":["CWE-94"],"updated_at":"2026-11-02T15:46:33.520522Z"},{"id":"GHSA-55hg-8qxv-qj4p","title":"PhoenixStorybook: Unauthenticated remote code execution via HEEx template injection in phoenix_storybook playground","description":"### Summary\nAn 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.\n\n### Details\nThe vulnerability is a three-step chain:\n\n**1. Unsanitized WebSocket input (`extra_assigns_helpers.ex`)**\nThe `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`.\n\n**2. Unescaped interpolation into HEEx (`component_renderer.ex`)**\n`ComponentRenderer.attributes_markup/1` builds a HEEx template string by interpolating binary attribute values directly:\n```elixir\n{name, val} when is_binary(val) -\u003e\n  ~s|#{name}=\"#{val}\"|\n```\nNo 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.\n\n**3. Unsandboxed evaluation (`component_renderer.ex`)**\nThe 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.\n\n### PoC\n1. Identify any story URL with a Playground tab (e.g. `/storybook/core_components/button`).\n2. Connect to the Phoenix LiveView WebSocket without any authentication.\n3. Join the story's LiveView channel and send a `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).\n4. The server evaluates the injected expression and returns its output in the rendered response.\n\nNo authentication, no special configuration, and no user interaction are required.\n\n### Impact\nThis 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.\n\n## Resources\n\n* Introduction Commit: https://github.com/phenixdigital/phoenix_storybook/commit/e35379dfe2ef1a71b141899e36f431017c55265d\n* Patch Commit: https://github.com/phenixdigital/phoenix_storybook/commit/56ab8464d4375fa52db806148a06cce126ad481d","status":"published","published":"2026-06-09T21:58:57Z","modified":"2026-06-09T22:15:08.050581956Z","cvss":[{"version":"4.0","score":9.5,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H","level":"critical"}],"cwes":["CWE-94"],"updated_at":"2026-11-02T15:46:37.864461Z"}]}}