{"id":"GHSA-vffh-c9pq-4crh","aliases":[],"status":"published","title":"Uptime Kuma Server-side Template Injection (SSTI) in Notification Templates Allows Arbitrary File Read","description":"### Summary\n\nIn some Notification types (e.g., Webhook, Telegram), the `send()` function allows user-controlled renderTemplate input. This leads to a Server-side Template Injection (SSTI) vulnerability that can be exploited to read arbitrary files from the server.\n\n\n\n### Details\n\nThe root cause is how Uptime Kuma renders user-controlled templates via `renderTemplate()`. The function instantiates a Liquid template engine and parses the `template` argument without sanitization:\n\n```js\nasync renderTemplate(template, msg, monitorJSON, heartbeatJSON) {\n    const engine = new Liquid();\n    const parsedTpl = engine.parse(template);\n\n    // ...\n}\n```\n\nIn some Notification flows, the `send()` implementation passes user-editable fields directly into `renderTemplate()`:\n```js\n// webhook.js\nif (notification.webhookContentType === \"form-data\") {\n    const formData = new FormData();\n    formData.append(\"data\", JSON.stringify(data));\n    config.headers = formData.getHeaders();\n    data = formData;\n} else if (notification.webhookContentType === \"custom\") {\n    data = await this.renderTemplate(notification.webhookCustomBody, msg, monitorJSON, heartbeatJSON); //\u003c- this line cause SSTI\n}\n```\n\nBecause `notification` can be edited by users and is rendered by the Liquid engine without proper sandboxing or a whitelist of allowed operations, an attacker can supply a crafted template that causes the server to read arbitrary files. In particular, Liquid’s template tags (e.g. `{% render ... %}`) can be abused to include server-side files if the engine is not restricted, resulting in Server-side Template Injection (SSTI) that leaks sensitive file contents.\n\n\n\n### PoC\n\n1. Open Uptime Kuma → **Notifications** → **Add** or **Edit** an existing Webhook notification.\n2. Set notification type to **Webhook** and set **Request Body**  to **Custom Body**.\n3. Paste the following JSON into the custom request body:\n\n```json\n{\n  \"Title\": {% render '/etc/passwd' %}\n}\n```\n\n4. Click test.\n5. Your webhook will receive the file content\n\n\n\n### Impact\n\nThis is a post-authentication Server-side Template Injection (SSTI) vulnerability that allows an authenticated user to perform arbitrary file read on the server.","severity":{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N","level":"medium","from":"ghsa"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-1336","CWE-36"],"published":"2025-10-20T20:03:15Z","modified":"2026-04-02T13:29:23Z","affected":[{"source":"ghsa","ecosystem":"npm","package":"uptime-kuma","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2.0.0-dev.0"},{"last_affected":"2.0.0-dev.0"}]}],"versions":["2.0.0-dev.0"]},{"source":"osv","ecosystem":"npm","package":"uptime-kuma","versions":["2.0.0-dev.0"]}],"references":[{"url":"https://github.com/louislam/uptime-kuma/security/advisories/GHSA-vffh-c9pq-4crh","tags":["web"]},{"url":"https://github.com/advisories/GHSA-vffh-c9pq-4crh"},{"url":"https://github.com/louislam/uptime-kuma","tags":["package"]}],"sources":{"ghsa":[{"id":"GHSA-vffh-c9pq-4crh","title":"Uptime Kuma Server-side Template Injection (SSTI) in Notification Templates Allows Arbitrary File Read","description":"### Summary\n\nIn some Notification types (e.g., Webhook, Telegram), the `send()` function allows user-controlled renderTemplate input. This leads to a Server-side Template Injection (SSTI) vulnerability that can be exploited to read arbitrary files from the server.\n\n\n\n### Details\n\nThe root cause is how Uptime Kuma renders user-controlled templates via `renderTemplate()`. The function instantiates a Liquid template engine and parses the `template` argument without sanitization:\n\n```js\nasync renderTemplate(template, msg, monitorJSON, heartbeatJSON) {\n    const engine = new Liquid();\n    const parsedTpl = engine.parse(template);\n\n    // ...\n}\n```\n\nIn some Notification flows, the `send()` implementation passes user-editable fields directly into `renderTemplate()`:\n```js\n// webhook.js\nif (notification.webhookContentType === \"form-data\") {\n    const formData = new FormData();\n    formData.append(\"data\", JSON.stringify(data));\n    config.headers = formData.getHeaders();\n    data = formData;\n} else if (notification.webhookContentType === \"custom\") {\n    data = await this.renderTemplate(notification.webhookCustomBody, msg, monitorJSON, heartbeatJSON); //\u003c- this line cause SSTI\n}\n```\n\nBecause `notification` can be edited by users and is rendered by the Liquid engine without proper sandboxing or a whitelist of allowed operations, an attacker can supply a crafted template that causes the server to read arbitrary files. In particular, Liquid’s template tags (e.g. `{% render ... %}`) can be abused to include server-side files if the engine is not restricted, resulting in Server-side Template Injection (SSTI) that leaks sensitive file contents.\n\n\n\n### PoC\n\n1. Open Uptime Kuma → **Notifications** → **Add** or **Edit** an existing Webhook notification.\n2. Set notification type to **Webhook** and set **Request Body**  to **Custom Body**.\n3. Paste the following JSON into the custom request body:\n\n```json\n{\n  \"Title\": {% render '/etc/passwd' %}\n}\n```\n\n4. Click test.\n5. Your webhook will receive the file content\n\n\n\n### Impact\n\nThis is a post-authentication Server-side Template Injection (SSTI) vulnerability that allows an authenticated user to perform arbitrary file read on the server.","status":"published","published":"2025-10-20T20:03:15Z","modified":"2025-10-20T20:03:19Z","cvss":[{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N","level":"medium"}],"cwes":["CWE-36","CWE-1336"],"updated_at":"2026-11-02T14:39:01.677422Z"}],"osv":[{"id":"GHSA-vffh-c9pq-4crh","title":"Uptime Kuma Server-side Template Injection (SSTI) in Notification Templates Allows Arbitrary File Read","description":"### Summary\n\nIn some Notification types (e.g., Webhook, Telegram), the `send()` function allows user-controlled renderTemplate input. This leads to a Server-side Template Injection (SSTI) vulnerability that can be exploited to read arbitrary files from the server.\n\n\n\n### Details\n\nThe root cause is how Uptime Kuma renders user-controlled templates via `renderTemplate()`. The function instantiates a Liquid template engine and parses the `template` argument without sanitization:\n\n```js\nasync renderTemplate(template, msg, monitorJSON, heartbeatJSON) {\n    const engine = new Liquid();\n    const parsedTpl = engine.parse(template);\n\n    // ...\n}\n```\n\nIn some Notification flows, the `send()` implementation passes user-editable fields directly into `renderTemplate()`:\n```js\n// webhook.js\nif (notification.webhookContentType === \"form-data\") {\n    const formData = new FormData();\n    formData.append(\"data\", JSON.stringify(data));\n    config.headers = formData.getHeaders();\n    data = formData;\n} else if (notification.webhookContentType === \"custom\") {\n    data = await this.renderTemplate(notification.webhookCustomBody, msg, monitorJSON, heartbeatJSON); //\u003c- this line cause SSTI\n}\n```\n\nBecause `notification` can be edited by users and is rendered by the Liquid engine without proper sandboxing or a whitelist of allowed operations, an attacker can supply a crafted template that causes the server to read arbitrary files. In particular, Liquid’s template tags (e.g. `{% render ... %}`) can be abused to include server-side files if the engine is not restricted, resulting in Server-side Template Injection (SSTI) that leaks sensitive file contents.\n\n\n\n### PoC\n\n1. Open Uptime Kuma → **Notifications** → **Add** or **Edit** an existing Webhook notification.\n2. Set notification type to **Webhook** and set **Request Body**  to **Custom Body**.\n3. Paste the following JSON into the custom request body:\n\n```json\n{\n  \"Title\": {% render '/etc/passwd' %}\n}\n```\n\n4. Click test.\n5. Your webhook will receive the file content\n\n\n\n### Impact\n\nThis is a post-authentication Server-side Template Injection (SSTI) vulnerability that allows an authenticated user to perform arbitrary file read on the server.","status":"published","published":"2025-10-20T20:03:15Z","modified":"2026-04-02T13:29:23.867333879Z","cvss":[{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N","level":"medium"}],"cwes":["CWE-1336","CWE-36"],"updated_at":"2026-11-02T15:46:57.348035Z"}]}}