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Claude Code's file access deny rules have significant bypasses

By PulseAugur Editorial · [3 sources] ·

New research indicates that Claude Code's file access deny rules are not as robust as initially assumed. While rules like `Read(.env)` effectively block the built-in Read tool, they do not prevent the model from accessing sensitive information through other means, such as the Bash tool executing commands like `grep` or Python scripts. This bypass occurs because Bash and other tools operate under different permission namespaces, and file path syntax can also lead to unintended access. The findings suggest that for true security, secrets should be kept outside the agent's working directory and potentially supplemented with pre-tool use hooks. AI

IMPACT Highlights potential security vulnerabilities in AI agent file access controls, necessitating stricter security practices for sensitive data.

RANK_REASON Analysis of a specific tool's security limitations and bypasses.

Read on dev.to — Claude Code tag →

AI-generated summary · Google Gemini · from 3 sources. How we write summaries →

Claude Code's file access deny rules have significant bypasses

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COVERAGE [3]

  1. dev.to — Claude Code tag TIER_1 English(EN) · Rulestack ·

    Claude Code read a file listed in .claudeignore 12 of 12 times; a Read deny rule blocked every read except grep -r

    <blockquote> <p>A <code>.claudeignore</code> entry changed nothing in Claude Code 2.1.289: the fake secret it listed came back in 12 of 12 attempts across Read, <code>cat</code>, <code>grep -r</code>, the Grep tool and an @-mention. A <code>Read(./secret.txt)</code> deny rule blo…

  2. dev.to — Claude Code tag TIER_1 English(EN) · jidonglab ·

    Claude Code Deny Rules Blocked Read(.env). Bash Read It Anyway

    <p>I added <code>Read(./.env)</code> to my deny list, felt responsible, and went back to work.</p> <p>An hour later I asked Claude Code why <code>DATABASE_URL</code> was undefined in my test runner. It tried the Read tool on <code>.env</code>, got refused, said "I can't read that…

  3. dev.to — Claude Code tag TIER_1 English(EN) · Rulestack ·

    Claude Code's Read deny rules let 4 of 11 routes through: grep -r, a Python one-liner and two CLAUDE.md @imports

    <blockquote> <p>4 of 11 routes to a file covered by <code>Read(./secrets/**)</code> or <code>Read(**/.env)</code> still put its contents in front of the model on Claude Code 2.1.285: <code>grep -r</code>, a Python one-liner, and an <code>@</code> import in a root or a subdirector…

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