CVE-2019-15790

Apport PID recycling exploit

• CVSS 3.3
• CWE-269
• Authentication, Authorization, and Session Management
• Local

Apport reads and writes information on a crashed process to /proc/pid with elevated privileges. Apport then determines which user the crashed process belongs to by reading /proc/pid through get_pid_info() in data/apport. An unprivileged user could exploit this to read information about a privileged running process by exploiting PID recycling. This information could then be used to obtain ASLR offsets for a process with an existing memory corruption vulnerability. The initial fix introduced regressions in the Python Apport library due to a missing argument in Report.add_proc_environ in apport/report.py. It also caused an autopkgtest failure when reading /proc/pid and with Python 2 compatibility by reading /proc maps. The initial and subsequent regression fixes are in 2.20.11-0ubuntu16, 2.20.11-0ubuntu8.6, 2.20.9-0ubuntu7.12, 2.20.1-0ubuntu2.22 and 2.14.1-0ubuntu3.29+esm3.

CVE

CVE-2019-15790

CWE

CWE-269

CVSS base score

3.3

Published

2020-04-28

OWASP

A07 Identification and Authentication Failures

Orthogonal defect classification

Function

Code defect classification

Incorrect Functionality

Category

Authentication, Authorization, and Session Management

Subcategory

Privilege Escalation

Accessibility scope

Local

Impact

Information Disclosure

Fixed by upgrading

Yes

Solution

Update Apport to version 2.20.11-0ubuntu16 or higher.

import os

def get_pid_info(pid):
    try:
        with open(f'/proc/{pid}/status') as f:
            return f.read()
    except FileNotFoundError:
        return None

def read_process_info(pid):
    proc_info = get_pid_info(pid)
    if proc_info:
        print(f"Process {pid} info:\n{proc_info}")
    else:
        print(f"No information found for PID {pid}")

import os
import pwd

def get_pid_info(pid):
    try:
        with open(f'/proc/{pid}/status') as f:
            status_info = f.read()
        uid = int(status_info.split('Uid:')[1].split()[0])
        user = pwd.getpwuid(uid).pw_name
        return user, status_info
    except FileNotFoundError:
        return None, None

def read_process_info(pid):
    user, status_info = get_pid_info(pid)
    if user is None:
        raise ValueError("Invalid PID or process does not exist.")
    
    current_user = pwd.getpwuid(os.getuid()).pw_name
    if user != current_user:
        raise PermissionError("Attempt to read information from a process owned by another user.")

    return status_info

@misc{vaitp:cve201915790,
  title        = {{Apport PID recycling exploit}},
  author       = {Bogaerts, Fr\'ed\'eric and Ivaki, Naghmeh and Fonseca, Jos\'e},
  year         = {2020},
  note         = {VAITP Python Vulnerability Dataset, entry CVE-2019-15790},
  howpublished = {\url{https://netpack.pt/vaitp/vulnerability/CVE-2019-15790/}}
}