Insecure Temporary File in /copy Command Enables Response Disclosure and Symlink-Based File Write

Medium4.4CVE-2026-46406 · Published Jun 25, 2026

The Claude Code `/copy` command wrote responses to a hardcoded, predictable path (`/tmp/claude/response.md`) without UID isolation, randomness, or symlink protection. The file was created world-readable (0644) in a world-traversable directory (0755), allowing any local user to read a privileged user's Claude response, which could contain secrets or credentials. Additionally, because the path was static and predictable, a local attacker could pre-create the directory and plant a symlink at the expected file path, causing the privileged process to follow the symlink and overwrite an attacker-chosen file with the response text. Exploiting this required a local unprivileged user on the same system and a privileged user to run the `/copy` command. Users on standard Claude Code auto-update have received this fix already. Users performing manual updates are advised to update to the latest version. Thank you to hackerone.com/c_h4ck_0 for reporting this issue.