CVE-2020-12695
Description
From CVE.org
The Open Connectivity Foundation UPnP specification before 2020-04-17 does not forbid the acceptance of a subscription request with a delivery URL on a different network segment than the fully qualified event-subscription URL, aka the CallStranger issue.
Statement
This flaw does not affect the wpa_supplicant package as shipped with Red Hat Enterprise Linux 5, 6, 7, and 8. wpa_supplicant's WiFi Protected Setup (WPS) External Registrar functionality, which uses UPnP to act as a registrar for a WiFi access point, and hostapd's WPS UPnP functionality, are disabled in the build configuration. Additionally, wpa_supplicant's P2P functionality does not support UPnP as shipped in Red Hat Enterprise Linux 5, 6, 7 and 8.
Mitigation
To mitigate this flaw, close off the UPnP UDP port (usually 1900) and UPnP service ports from the Internet using a firewall. It's important to note that UPnP service ports vary based on the device, so device documentation should be consulted. Do not expose UPnP servers to the Internet. Exploitation of this flaw relies on HTTP SUBSCRIBE and NOTIFY requests, which can be blocked using a network security appliance, as another mitigation option.
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 | 7.5 | 7.5 | N/A |
| Attack Vector | Network | Network | N/A |
| Attack Complexity | High | High | N/A |
| Privileges Required | None | None | N/A |
| User Interaction | None | None | N/A |
| Scope | Changed | Changed | N/A |
| Confidentiality | Low | Low | N/A |
| Integrity Impact | None | None | N/A |
| Availability Impact | High | High | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:N/A:H
NVD: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:N/A:H
Red Hat CVSS v3 Score Explanation
Marked AC:H because an attacker needs factors outside of his/her/their control in order to exploit the flaw. Such factors include a public-facing UPnP server or local/adjacent network access to a UPnP server. Without direct access to the UPnP server, the attacks are not possible.
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Application Data
Integrity
Technical Impact: Execute Unauthorized Code or Commands
Access Control
Technical Impact: Bypass Protection Mechanism
By providing URLs to unexpected hosts or ports, attackers can make it appear that the server is sending the request, possibly bypassing access controls such as firewalls that prevent the attackers from accessing the URLs directly. The server can be used as a proxy to conduct port scanning of hosts in internal networks, use other URLs such as that can access documents on the system (using file://), or use other protocols such as gopher:// or tftp://, which may provide greater control over the contents of requests.
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