Full Report
Cybersecurity researchers have disclosed details of a now-patched security flaw in the Amazon EC2 Simple Systems Manager (SSM) Agent that, if successfully exploited, could permit an attacker to achieve privilege escalation and code execution. The vulnerability could permit an attacker to create directories in unintended locations on the filesystem, execute arbitrary scripts with root privileges,
Analysis Summary
# Vulnerability: Amazon EC2 SSM Agent Path Traversal Leading to Privilege Escalation
## CVE Details
- CVE ID: Not explicitly provided in the text (Implied vulnerability in SSM Agent)
- CVSS Score: Not explicitly provided
- CWE: CWE-22 (Improper Limitation of a Pathname to a Restricted Segment of a Physical File System)
## Affected Systems
- Products: Amazon EC2 Simple Systems Manager (SSM) Agent
- Versions: Prior to version 3.3.1957.0
- Configurations: Any configuration where the SSM Agent processes user-supplied input for plugin IDs without proper sanitization.
## Vulnerability Description
The vulnerability is a path traversal flaw rooted in the `ValidatePluginId` function within `pluginutil.go` of the Amazon SSM Agent. This function fails to properly sanitize plugin IDs provided in SSM Documents. An attacker can supply a specially crafted path traversal sequence (e.g., `../`) within the plugin ID to manipulate the filesystem, allowing them to create directories in unintended locations, potentially writing files to sensitive system areas, and enabling arbitrary code execution with root privileges.
## Exploitation
- Status: Details suggest the potential for exploitation leading to privilege escalation, though it is not explicitly stated as being exploited in the wild. The research confirms exploitability.
- Complexity: Not explicitly rated, but exploitation relies on crafting malicious SSM document parameters, suggesting **Medium** complexity for a full RCE/privilege escalation chain.
- Attack Vector: **Local** (Requires an entity capable of creating or manipulating SSM Documents that the agent will process) or potentially **Network** if the initial access allows creation of these documents.
## Impact
- Confidentiality: High (If attacker can read sensitive configuration files or execution context)
- Integrity: High (Ability to modify system files or arbitrary code execution)
- Availability: High (Ability to disrupt service or compromise the system configuration)
## Remediation
### Patches
- Amazon SSM Agent **version 3.3.1957.0** or later. The fix implemented the use of a `BuildSafePath` method to prevent path traversal in the orchestration directory.
### Workarounds
- No explicit workarounds are detailed, however, the implied mitigation before patching is to strictly validate and reject any plugin IDs containing path traversal sequences (`../`, etc.) if custom document creation is managed by external users.
## Detection
- Indicators of compromise would involve unusual directory creation or file modifications within the directories managed by the SSM Agent, particularly processes attempting to write outside expected operational folders using escalated privileges.
- Detection methods should focus on monitoring SSM Agent behavior and network traffic related to SSM document distribution for malicious parameters being passed to the agent's input handlers.
## References
- Vendor Advisory: Amazon SSM Agent release notes detailing version 3.3.1957.0 (Linked on GitHub)
- Research Report: cymulate dot com slash blog slash aws-ssm-agent-plugin-id-path-traversal slash (Defanged based on source context)
- GitHub Release: aws slash amazon-ssm-agent slash releases slash tag slash 3 dot 3 dot 1957 dot 0 (Defanged based on source context)