CVE-2021-39597 - NULL Pointer Dereference

Severity

55%

Complexity

18%

Confidentiality

60%

An issue was discovered in swftools through 20200710. A NULL pointer dereference exists in the function code_dump2() located in code.c. It allows an attacker to cause Denial of Service.

CVSS 3.1 Base Score 5.5. CVSS Attack Vector: local. CVSS Attack Complexity: low. CVSS Vector: (CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H).

CVSS 2.0 Base Score 4.3. CVSS Attack Vector: network. CVSS Attack Complexity: medium. CVSS Vector: (AV:N/AC:M/Au:N/C:N/I:N/A:P).

Demo Examples

NULL Pointer Dereference

CWE-476

While there are no complete fixes aside from conscientious programming, the following steps will go a long way to ensure that NULL pointer dereferences do not occur.


               
}
/* make use of pointer1 *//* ... */

If you are working with a multithreaded or otherwise asynchronous environment, ensure that proper locking APIs are used to lock before the if statement; and unlock when it has finished.

NULL Pointer Dereference

CWE-476

This example takes an IP address from a user, verifies that it is well formed and then looks up the hostname and copies it into a buffer.


               
}
strcpy(hostname, hp->h_name);/*routine that ensures user_supplied_addr is in the right format for conversion */

If an attacker provides an address that appears to be well-formed, but the address does not resolve to a hostname, then the call to gethostbyaddr() will return NULL. Since the code does not check the return value from gethostbyaddr (CWE-252), a NULL pointer dereference would then occur in the call to strcpy().

Note that this example is also vulnerable to a buffer overflow (see CWE-119).

NULL Pointer Dereference

CWE-476

In the following code, the programmer assumes that the system always has a property named "cmd" defined. If an attacker can control the program's environment so that "cmd" is not defined, the program throws a NULL pointer exception when it attempts to call the trim() method.


               
cmd = cmd.trim();

NULL Pointer Dereference

CWE-476

This application has registered to handle a URL when sent an intent:


               
}......
}
}
int length = URL.length();
...

The application assumes the URL will always be included in the intent. When the URL is not present, the call to getStringExtra() will return null, thus causing a null pointer exception when length() is called.

Overview

First reported 1 month ago

2021-09-20 16:15:00

Last updated 1 month ago

2021-09-22 18:15:00

Affected Software

SWFTools

Stay updated

ExploitPedia is constantly evolving. Sign up to receive a notification when we release additional functionality.

Get in touch

If you'd like to report a bug or have any suggestions for improvements then please do get in touch with us using this form. We will get back to you as soon as we can.