Overview
CVE-2025-64755 identifies a security vulnerability in Claude Code, an agentic coding tool. Prior to version 2.0.31, a flaw in the parsing of sed commands allowed attackers to bypass the intended read-only validation mechanisms. This bypass could potentially lead to arbitrary file writes on the host system, posing a significant security risk.
Technical Details
The vulnerability stems from improper sanitization or validation of user-supplied input used in constructing sed commands. Specifically, a specially crafted input string could manipulate the sed command’s behavior, circumventing the intended restrictions and allowing write operations to locations outside the designated read-only areas. The exact mechanism of the bypass likely involves exploiting how sed handles metacharacters or command injection within the input string. A detailed explanation of the exploit is available at the provided GitHub security advisory. Understanding the specific syntax used in the exploit is crucial for comprehending the vulnerability’s impact and developing effective defenses.
CVSS Analysis
While the CVE entry lists the severity and CVSS score as “N/A”, the potential for arbitrary file writes generally indicates a high-severity vulnerability. A missing CVSS score doesn’t diminish the risk. Security professionals should assess the vulnerability based on the context of their specific Claude Code deployment.
Possible Impact
Successful exploitation of CVE-2025-64755 could have severe consequences, including:
- Data Breach: Sensitive data stored in files accessible to the compromised Claude Code instance could be exposed.
- System Compromise: Writing to critical system files could lead to system instability, denial of service, or even complete system compromise.
- Malware Installation: An attacker could write malicious executables to the system, leading to further exploitation and control.
- Privilege Escalation: Depending on the file permissions and context, the attacker might be able to escalate their privileges on the system.
Mitigation or Patch Steps
The primary mitigation for CVE-2025-64755 is to upgrade to Claude Code version 2.0.31 or later. The patch implemented in this version addresses the improper sed command parsing and prevents the read-only bypass. If upgrading is not immediately feasible, consider implementing temporary workarounds, such as:
- Input Validation: Implement rigorous input validation and sanitization on all data provided to Claude Code, specifically targeting characters and sequences known to be problematic in
sedcommands. - Restrict Permissions: Limit the permissions of the Claude Code process to only access the necessary files and directories, minimizing the potential damage from a successful exploit.
- Monitor System Activity: Monitor system logs and file system activity for any suspicious behavior that might indicate an attempted exploit.
However, these workarounds are not a substitute for upgrading to the patched version.
