Security: Mode tracker flag file write also vulnerable to symlink-based overwrite#71
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JuliusBrussee merged 1 commit intoJuliusBrussee:mainfrom Apr 15, 2026
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The UserPromptSubmit hook similarly writes to `~/.claude/.caveman-active` without checking whether the path is a symlink. This duplicates the same local file-clobber risk in another execution path. Affected files: caveman-mode-tracker.js Signed-off-by: tuanaiseo <221258316+tuanaiseo@users.noreply.github.com>
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…ession Writes were hardened via safeWriteFlag (PRs #70/#71) but readers still trusted whatever the flag contained. A local attacker with write access to ~/.claude/ could symlink the flag at a secret file and have the per-turn reinforcement inject its bytes into model context, or the statuslines echo ANSI escapes to the terminal on every keystroke. - caveman-config.js: new readFlag() — lstat symlink refuse, 64-byte cap, O_NOFOLLOW, VALID_MODES whitelist. Returns null on any anomaly. - caveman-mode-tracker.js: per-turn reinforcement routes through readFlag() instead of fs.readFileSync. - caveman-statusline.sh / .ps1: symlink + size refuse, strip to [a-z0-9-], whitelist-validate before rendering. - compress.py (3 synced copies): is_sensitive_path() denylist refuses .env*, .netrc, keys/certs, ~/.ssh|.aws|.gnupg|.kube|.docker, and any basename containing secret/credential/password/apikey/token/privatekey (separator-insensitive). Fails loudly before read — no silent exfil of credentials to the Anthropic API. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Problem
The UserPromptSubmit hook similarly writes to
~/.claude/.caveman-activewithout checking whether the path is a symlink. This duplicates the same local file-clobber risk in another execution path.Severity:
mediumFile:
hooks/caveman-mode-tracker.jsSolution
Apply the same hardening as in the activation hook: validate path components with
lstat, refuse symlinks, and write with restrictive permissions and atomic replace semantics.Changes
hooks/caveman-mode-tracker.js(modified)Testing