CVE-2020-13398
Description
An issue was found in freerdp's libfreerdp/crypto/crypto.c, in versions before 2.1.1, where buffer access with an incorrect length value, leads to an out-of-bounds write. This flaw allows a remote, unauthenticated, attacker running an RDP server, or a local attacker, using a specially crafted certificate, to cause an out-of-bounds write into client process memory, corrupting the integrity of the data used in the RSA encryption functionality, or causing a denial of service.
Mitigation
To mitigate this flaw, only make connection attempts to trusted RDP servers from the RDP client application.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 8.3 | 8.3 | N/A |
| Attack Vector | Network | Network | N/A |
| Attack Complexity | Low | Low | N/A |
| Privileges Required | Low | Low | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | High | High | N/A |
| Integrity Impact | High | High | N/A |
| Availability Impact | Low | Low | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:L
NVD: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:L
Red Hat CVSS v3 Score Explanation
The above score differs in:
I:H because this is an out-of-bounds write in the RSA cryptography code which could affect the integrity of the cryptography used. A:L because a heap buffer overflow -> out-of-bounds write is undefined behavior and could crash the program. AV:N because the RDP server's certificate fields are used as input for the vulnerable component, which is obtained via a network.
Understanding the Weakness (CWE)
Integrity,Confidentiality,Availability
Technical Impact: Read Memory; Modify Memory; Execute Unauthorized Code or Commands
Buffer overflows often can be used to execute arbitrary code, which is usually outside the scope of a program's implicit security policy. This can often be used to subvert any other security service.
Availability
Technical Impact: Modify Memory; DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU)
Buffer overflows generally lead to crashes. Other attacks leading to lack of availability are possible, including putting the program into an infinite loop.
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