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The vulnerability in the anthropic-ai/claude-code platform stems from an insufficient validation mechanism for sed commands. The system’s read-only validation, intended to restrict file modifications, can be bypassed through cleverly crafted sed command arguments. An attacker can exploit improper parsing of these commands to break out of the intended constraints. This is achieved by injecting arguments that manipulate the sed processing flow, such as using the `-e` flag to append multiple expressions or the `-i` flag for in-place editing, which may not be adequately sanitized. Consequently, the sed command executes with higher privileges than intended, allowing the attacker to perform write operations on arbitrary files within the host system’s filesystem, leading to a compromise of integrity and potential remote code execution.
Platform: anthropic-ai/claude-code
Version: pre-auto-update fix
Vulnerability: Arbitrary File Write
Severity: High
date: 2025-11-20
Prediction: Patch expected 2025-11-27
What Undercode Say:
sed -i 's/readonly_flag//g' /etc/passwd
sed -e '1d' -e 's/root/toor/' sensitive_file
Example of potentially vulnerable command construction user_input = " -i backup s/old/new/g /path/to/target" cmd = "sed" + user_input subprocess.call(cmd, shell=True)
How Exploit:
Craft sed command arguments to bypass read-only checks and write to critical system files like /etc/passwd or application configuration files, potentially leading to privilege escalation or system compromise.
Protection from this CVE:
Update Claude Code. Implement strict input validation and whitelist allowed sed flags. Use subprocess without shell=True. Employ proper sandboxing.
Impact:
Arbitrary file overwrite, system integrity loss, possible remote code execution, and full host compromise depending on the context and privileges of the Claude Code process.
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Sources:
Reported By: github.com
Extra Source Hub:
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