NewsPublished 7 May 2026

Claude Code OAuth Tokens Can Be Stolen Through Stealthy MCP Hijacking

Source SecurityWeek

Description

Mitiga researchers say attackers can silently redirect Claude Code MCP traffic, intercept OAuth tokens, and maintain persistent access to connected SaaS platforms. The post Claude Code OAuth Tokens Can Be Stolen Through Stealthy MCP Hijacking appeared first on SecurityWeek .

Impact

An attacker who successfully exploits this vulnerability can steal OAuth tokens that serve as master keys to all SaaS platforms connected through Claude Code's MCP. This enables persistent, stealthy access to victim SaaS accounts with the same permissions as the user, bypassing multi-factor authentication. The victim remains unaware as the attack does not disrupt normal operation or trigger visible alerts. The attacker can maintain access even after token rotation or configuration changes, posing a significant risk of unauthorized data access and potential lateral movement within connected SaaS environments.

Defensive guidance

Mitiga recommends monitoring Claude Code configuration changes, especially modifications to the MCP server URL and the ~/.claude.json file, as well as observing OAuth token refresh behavior and suspicious SaaS API activity. Users should be cautious about installing untrusted npm packages and consider restricting or auditing npm package installations on machines running Claude Code. Since the vulnerability relies on local compromise, endpoint security controls to prevent unauthorized software installation can reduce risk.

References

securityweek.com/claude-code-oauth-tokens-can-be-stolen-through-stealthy-mcp-hijacking/ (opens in a new tab)

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Description

AI analysisMachine-generated, updated 7 May 2026, 14:36 UTC

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