Amazon Q Developer Flaw Exposed Cloud Credentials via Malicious Repo Configs
A high-severity vulnerability in Amazon Q Developer allowed attackers to execute arbitrary code and steal cloud credentials through malicious Model Context Protocol configurations. Amazon has patched CVE-2026-12957 (CVSS 8.5) following responsible disclosure.
TL;DR
- CVE-2026-12957 (CVSS 8.5) in Amazon Q Developer enabled code execution and credential theft via MCP server mishandling
- Attack chain required minimal user interaction: opening a malicious repo and trusting the workspace triggered automatic exploitation
- Vulnerability resided in how the AI assistant processed Model Context Protocol configurations without sufficient validation
- Amazon has released a patch; developers should update immediately to prevent supply-chain compromise risks
Amazon Q Developer, an AI-powered coding assistant, contained a high-severity flaw that could allow attackers to execute arbitrary commands and exfiltrate cloud credentials from developer environments. Tracked as CVE-2026-12957 with a CVSS score of 8.5, the vulnerability stemmed from improper handling of Model Context Protocol (MCP) server configurations.
The attack surface was deceptively simple: a developer needed only to open a repository containing malicious MCP configurations and trust the workspace. Once those conditions were met, Amazon Q would automatically process the attacker-controlled protocol settings, leading to code execution and credential compromise.
Amazon has released a patch addressing the flaw. Development teams should prioritize updating to mitigate the risk of supply-chain attacks through compromised or malicious repositories.
Vulnerability Details and Attack Vector
- CVE-2026-12957 exploited insufficient validation of Model Context Protocol (MCP) server configurations in Amazon Q Developer
- Attack required minimal user interaction: opening a malicious repository and trusting the workspace triggered automatic exploitation
- Successful exploitation enabled arbitrary command execution and theft of developer cloud credentials
- CVSS 8.5 rating reflects the high severity and ease of exploitation in typical development workflows
Risk and Remediation
- Malicious repositories could compromise individual developer credentials and potentially provide lateral movement into cloud infrastructure
- Supply-chain risk amplified if compromised code or repositories are shared across development teams
- Amazon has released a patch; all users should update Amazon Q Developer immediately
- Development teams should audit recent repository access and review cloud credential usage for signs of unauthorized activity
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