CVE-2021-44224
Description
There's a null pointer dereference and server-side request forgery flaw in httpd's mod_proxy module, when it is configured to be used as a forward proxy. A crafted packet could be sent on the adjacent network to the forward proxy that could cause a crash, or potentially SSRF via misdirected Unix Domain Socket requests. In the worst case, this could cause a denial of service or compromise to confidentiality of data.
Statement
This flaw does not affect httpd configurations that do not use forward proxy functionality (configurations where ProxyRequests is turned off).
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.
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 | 7.1 | 8.2 | N/A |
| Attack Vector | Adjacent Network | Network | N/A |
| Attack Complexity | High | Low | N/A |
| Privileges Required | Low | None | N/A |
| User Interaction | None | None | N/A |
| Scope | Changed | Unchanged | N/A |
| Confidentiality | Low | None | N/A |
| Integrity Impact | Low | Low | N/A |
| Availability Impact | High | High | N/A |
Vector
Red Hat: CVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:C/C:L/I:L/A:H
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
Red Hat CVSS v3 Score Explanation
AV:A as forward proxy is generally used in an intranet, AC:H because an attacker may not necessarily have at-will access to the intranet and would also need a mixed forward/reverse proxy configuration to exploit the potential SSRF, which is not in the attacker's direct control. However, if the SSRF was exploited it could lead to scope change via gaining access to resources managed by other security authorities under the guise of the Apache server, hence S:C and C:L.
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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