CVE-2026-108258: Shiny Path Traversal Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-47c3-hpmg-7j6p",
  "modified" : "2026-10-09T20:56:37Z",
  "published" : "2026-10-09T20:56:37Z",
  "aliases" : [ "CVE-2026-108258" ],
  "summary" : "Shiny for Python has path traversal in bookmark restore",
  "details" : "### Impact\n\nShiny for Python's bookmark-restore path accepted a client-supplied `_state_id_`\nquery-string value and joined it into the server-side bookmark directory\n(`<cwd>/shiny_bookmarks/<id>`) without validating it. A value containing `..`\npath segments, or an absolute path, could therefore cause the server to open and\nparse `input.json` and `values.json` from a directory outside the bookmark store.\n\nOn a default application the restore was attempted whenever the client supplied a\nURL query string — including when bookmarking was disabled\n(`bookmark_store=\"disable\"`) — so no opt-in configuration was required. For such\napplications the impact is an unauthenticated, server-side probe for the\nexistence and JSON-validity of attacker-chosen paths, constrained to those two\nfile names.\n\nApplications configured with `bookmark_store=\"server\"` **and** using\n`ui.input_file()` are affected more seriously. The file-input restore handler\ncopies files out of the restore directory, so the contents of an\nattacker-selected file name within an attacker-selected directory could be read\ninto the application.\n\n### Affected versions\n\n1.4.0 through 1.6.3. Bookmarking was introduced in 1.4.0; earlier releases do\nnot contain the affected code path and are not affected.\n\n### Patches\n\nFixed in **1.6.4**. Upgrade with:\n\n```\npip install --upgrade shiny\n```\n\nThe fix validates bookmark IDs against an allowlist — a single path segment\nmatching `[A-Za-z0-9_-]+`, which cannot express a path separator, a `..` parent\nreference, or an absolute path — before the ID is used to build a filesystem\npath. Bookmark IDs generated by Shiny are unaffected by this restriction.\nRestore is additionally gated on the application's `bookmark_store` setting at a\nsingle point, so it no longer runs when bookmarking is disabled, and the on-disk\nrestore path is honored only under `bookmark_store=\"server\"`.\n\n### Workarounds\n\nThere is no configuration change that mitigates this on an affected version:\nthe restore path ran even with `bookmark_store=\"disable\"`. Deployments that\ncannot upgrade immediately can strip the `_state_id_` parameter from incoming\nquery strings at a reverse proxy or load balancer, which prevents the affected\ncode path from being reached.\n\n### Credits\n\nReported by [@0xRenSec](https://github.com/0xRenSec).",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "shiny"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.4.0"
      }, {
        "fixed" : "1.6.4"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 1.6.3"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/posit-dev/py-shiny/security/advisories/GHSA-47c3-hpmg-7j6p"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/posit-dev/py-shiny/commit/1d8ecb46cbc9621b7dc8812111d26692e086b376"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/posit-dev/py-shiny"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/posit-dev/py-shiny/releases/tag/v1.6.4"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-22" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-10-09T20:56:37Z",
    "nvd_published_at" : null
  }
}