CVE-2020-13529
Description
An exploitable denial of service vulnerability exists in systemd which does not fully implement RFC3203, as it does not support authentication of FORCERENEW packets. A specially crafted DHCP FORCERENEW packet can cause a system, running the DHCP client, to be vulnerable to a DHCP ACK spoofing attack. An attacker can forge a pair of FORCERENEW and DCHPACK packets to reconfigure the system with arbitrary network settings.
Statement
This issue did not affect the versions of systemd as shipped with Red Hat Enterprise Linux 8 as they did not include systemd-networkd service.
NetworkManager embeds some pieces of systemd code base, including the DHCP client code. For this reason NetworkManager is marked as affected. By default only the versions of NetworkManager as shipped in Red Hat Enterprise Linux 8.0 and 8.1 are affected, as in those versions NetworkManager uses main.dhcp=internal setting (see networkmanager.conf(5)) by default, which relies on systemd DHCP client. On newer Red Hat Enterprise Linux 8 versions NetworkManager uses a different DHCP client by default, which is not affected by this flaw. On Red Hat Enterprise Linux 7 NetworkManager uses main.dhcp=dhclient by default, which is not affected by this flaw either, however users who have explicitly configured main.dhcp=internal would be affected, as the systemd DHCP client would be used in that case.
Mitigation
There is no available mitigation for this issue.
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 | 6.1 | 6.1 | 6.1 |
| Attack Vector | Adjacent Network | Adjacent Network | Adjacent Network |
| Attack Complexity | High | High | High |
| Privileges Required | None | None | None |
| User Interaction | None | None | None |
| Scope | Changed | Changed | Changed |
| Confidentiality | None | None | None |
| Integrity Impact | None | None | None |
| Availability Impact | High | High | High |
Vector
Red Hat: CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H
NVD: CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H
cve.org: CVSS:3.0/AV:A/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H
Understanding the Weakness (CWE)
Access Control,Other
Technical Impact: Gain Privileges or Assume Identity; Varies by Context
Exposing critical functionality essentially provides an attacker with the privilege level of that functionality. The consequences will depend on the associated functionality, but they can range from reading or modifying sensitive data, accessing administrative or other privileged functionality, or possibly even executing arbitrary code.
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