CVE-2020-25667 - Out-of-bounds Read

Severity

55%

Complexity

18%

Confidentiality

60%

TIFFGetProfiles() in /coders/tiff.c calls strstr() which causes a large out-of-bounds read when it searches for `"dc:format=\"image/dng\"` within `profile` due to improper string handling, when a crafted input file is provided to ImageMagick. The patch uses a StringInfo type instead of a raw C string to remedy this. This could cause an impact to availability of the application. This flaw affects ImageMagick versions prior to 7.0.9-0.

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

Out-of-bounds Read

CWE-125

In the following code, the method retrieves a value from an array at a specific array index location that is given as an input parameter to the method


               
}
return value;// check that the array index is less than the maximum// length of the array
value = array[index];// get the value at the specified index of the array
// if array index is invalid then output error message// and return value indicating error
value = -1;

However, this method only verifies that the given array index is less than the maximum length of the array but does not check for the minimum value (CWE-839). This will allow a negative value to be accepted as the input array index, which will result in a out of bounds read (CWE-125) and may allow access to sensitive memory. The input array index should be checked to verify that is within the maximum and minimum range required for the array (CWE-129). In this example the if statement should be modified to include a minimum range check, as shown below.


               
...// check that the array index is within the correct// range of values for the array

Demo Examples

Heap-based Buffer Overflow

CWE-122

While buffer overflow examples can be rather complex, it is possible to have very simple, yet still exploitable, heap-based buffer overflows:


               
}
strcpy(buf, argv[1]);

The buffer is allocated heap memory with a fixed size, but there is no guarantee the string in argv[1] will not exceed this size and cause an overflow.

Heap-based Buffer Overflow

CWE-122

This example applies an encoding procedure to an input string and stores it into a buffer.


               
}
return dst_buf;
die("user string too long, die evil hacker!");
else dst_buf[dst_index++] = user_supplied_string[i];
dst_buf[dst_index++] = ';';
/* encode to < */

The programmer attempts to encode the ampersand character in the user-controlled string, however the length of the string is validated before the encoding procedure is applied. Furthermore, the programmer assumes encoding expansion will only expand a given character by a factor of 4, while the encoding of the ampersand expands by 5. As a result, when the encoding procedure expands the string it is possible to overflow the destination buffer if the attacker provides a string of many ampersands.

Overview

First reported 4 years ago

2020-12-08 21:15:00

Last updated 4 years ago

2020-12-10 16:06:00

Affected Software

ImageMagick

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