CVE-2019-12455 - NULL Pointer Dereference

Severity

49%

Complexity

39%

Confidentiality

115%

** DISPUTED ** An issue was discovered in sunxi_divs_clk_setup in drivers/clk/sunxi/clk-sunxi.c in the Linux kernel through 5.1.5. There is an unchecked kstrndup of derived_name, which might allow an attacker to cause a denial of service (NULL pointer dereference and system crash). NOTE: This id is disputed as not being an issue because “The memory allocation that was not checked is part of a code that only runs at boot time, before user processes are started. Therefore, there is no possibility for an unprivileged user to control it, and no denial of service.”.

** DISPUTED ** An issue was discovered in sunxi_divs_clk_setup in drivers/clk/sunxi/clk-sunxi.c in the Linux kernel through 5.1.5. There is an unchecked kstrndup of derived_name, which might allow an attacker to cause a denial of service (NULL pointer dereference and system crash). NOTE: This id is disputed as not being an issue because “The memory allocation that was not checked is part of a code that only runs at boot time, before user processes are started. Therefore, there is no possibility for an unprivileged user to control it, and no denial of service.”.

CVSS 3.0 Base Score 5.5. CVSS Attack Vector: local. CVSS Attack Complexity: low. CVSS Vector: (CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H).

CVSS 2.0 Base Score 4.9. CVSS Attack Vector: local. CVSS Attack Complexity: low. CVSS Vector: (AV:L/AC:L/Au:N/C:N/I:N/A:C).

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.

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