OS Command Injection in Amazon awslabs Postgres-MCP-Server 1.1.6 Read-Only Mode
CVE-2026-87911 Published on September 9, 2026
Read-only enforcement bypass enabling operating system command execution in the SQL validation component of Amazon awslabs postgres-mcp-server
An OS command injection weakness in the read-only enforcement of the SQL validation component in Amazon awslabs postgres-mcp-server before 1.1.7 might allow an unauthenticated actor to execute operating system commands on the host of a self-managed PostgreSQL server by placing a crafted COPY ... TO PROGRAM statement into content that is processed when an authenticated user interacts with the MCP server in its default read-only mode.
To remediate this issue, users should upgrade to version 1.1.7 or later.
Vulnerability Analysis
CVE-2026-87911 can be exploited with network access, requires user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to be critical as this vulnerability has a high impact to the confidentiality, integrity and availability of this component.
Weakness Types
What is a Shell injection Vulnerability?
The software constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component.
CVE-2026-87911 has been classified to as a Shell injection vulnerability or weakness.
What is a Denylist / Deny List Vulnerability?
The product implements a protection mechanism that relies on a list of inputs (or properties of inputs) that are not allowed by policy or otherwise require other action to neutralize before additional processing takes place, but the list is incomplete, leading to resultant weaknesses. Developers often try to protect their products against malicious input by performing tests against inputs that are known to be bad, such as special characters that can invoke new commands. However, such lists often only account for the most well-known bad inputs. Attackers may be able to find other malicious inputs that were not expected by the developer, allowing them to bypass the intended protection mechanism.
CVE-2026-87911 has been classified to as a Denylist / Deny List vulnerability or weakness.
Products Associated with CVE-2026-87911
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Affected Versions
AWS Labs postgres MCP Server:- Before 1.1.7 is affected.