CVE-2020-6096 - Integer Underflow (Wrap or Wraparound)

Severity

81%

Complexity

22%

Confidentiality

98%

An exploitable signed comparison vulnerability exists in the ARMv7 memcpy() implementation of GNU glibc 2.30.9000. Calling memcpy() (on ARMv7 targets that utilize the GNU glibc implementation) with a negative value for the 'num' parameter results in a signed comparison vulnerability. If an attacker underflows the 'num' parameter to memcpy(), this vulnerability could lead to undefined behavior such as writing to out-of-bounds memory and potentially remote code execution. Furthermore, this memcpy() implementation allows for program execution to continue in scenarios where a segmentation fault or crash should have occurred. The dangers occur in that subsequent execution and iterations of this code will be executed with this corrupted data.

An exploitable signed comparison vulnerability exists in the ARMv7 memcpy() implementation of GNU glibc 2.30.9000. Calling memcpy() (on ARMv7 targets that utilize the GNU glibc implementation) with a negative value for the 'num' parameter results in a signed comparison vulnerability. If an attacker underflows the 'num' parameter to memcpy(), this vulnerability could lead to undefined behavior such as writing to out-of-bounds memory and potentially remote code execution. Furthermore, this memcpy() implementation allows for program execution to continue in scenarios where a segmentation fault or crash should have occurred. The dangers occur in that subsequent execution and iterations of this code will be executed with this corrupted data.

CVSS 3.1 Base Score 8.1. CVSS Attack Vector: network. CVSS Attack Complexity: high. CVSS Vector: (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H).

CVSS 2.0 Base Score 6.8. CVSS Attack Vector: network. CVSS Attack Complexity: medium. CVSS Vector: (AV:N/AC:M/Au:N/C:P/I:P/A:P).

Demo Examples

Integer Underflow (Wrap or Wraparound)

CWE-191

The following example subtracts from a 32 bit signed integer.


               
}
return 0;

The example has an integer underflow. The value of i is already at the lowest negative value possible, so after subtracting 1, the new value of i is 2147483647.

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