CVE-2023-38408
Description
A vulnerability was found in OpenSSH. The PKCS#11 feature in the ssh-agent in OpenSSH has an insufficiently trustworthy search path, leading to remote code execution if an agent is forwarded to an attacker-controlled system (the code in /usr/lib is not necessarily safe for loading into ssh-agent). This flaw allows an attacker with control of the forwarded agent-socket on the server and the ability to write to the filesystem of the client host to execute arbitrary code with the privileges of the user running the ssh-agent.
Statement
This issue is marked as Important as we successfully identified that it can do a Remote Code Execution atleast at some circumstances in Red Hat Enterprise Linux 6, 7, 8 and 9 and It can easily compromise the confidentiality, integrity or availability of resources.
Mitigation
Remote exploitation required that a user establishes an SSH connection to a compromised or malicious SSH server with agent forwarding enabled. The agent forwarding is disabled by default. Review your ssh client configuration files for the use of ForwardAgent configuration directive and invocations of ssh client for the use of -A command line argument to see if agent forwarding is enabled for specific connections.
Exploitation can also be prevented by starting ssh-agent(1) with an empty PKCS#11/FIDO allowlist (ssh-agent -P '') or by configuring an allowlist that contains only specific provider libraries.
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 | 9.8 | 9.8 | N/A |
| Attack Vector | Network | Network | N/A |
| Attack Complexity | Low | Low | N/A |
| Privileges Required | None | None | 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 | High | High | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Understanding the Weakness (CWE)
Access Control
Technical Impact: Bypass Protection Mechanism
In some cases, injectable code controls authentication; this may lead to a remote vulnerability.
Access Control
Technical Impact: Gain Privileges or Assume Identity
Injected code can access resources that the attacker is directly prevented from accessing.
Integrity,Confidentiality,Availability
Technical Impact: Execute Unauthorized Code or Commands
When a product allows a user's input to contain code syntax, it might be possible for an attacker to craft the code in such a way that it will alter the intended control flow of the product. As a result, code injection can often result in the execution of arbitrary code. Code injection attacks can also lead to loss of data integrity in nearly all cases, since the control-plane data injected is always incidental to data recall or writing.
Non-Repudiation
Technical Impact: Hide Activities
Often the actions performed by injected control code are unlogged.
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