Python EUVD-2026-32664

Summary

tools/quota-statusline.sh (introduced in v3.5.0) interpolates Claude Code's hook stdin payload directly into a Python triple-quoted string literal. A ''' byte sequence in any user-controlled field of the payload closes the literal early and lets following bytes execute as Python in the user's Claude Code process.

Affected versions

• v3.5.0
• v3.5.1

Patched versions

• v3.5.2

Affected configurations

Users who wired tools/quota-statusline.sh into Claude Code's statusLine configuration. The v3.5.0 README explicitly recommends this setup, so most users on v3.5.0/v3.5.1 with the recommended setup are affected.

Attack chain

Claude Code's statusline hook payload reflects user-controlled paths (cwd, workspace.current_dir, workspace.project_dir, transcript_path). Apostrophes are legal in POSIX filesystem paths.

1. A hostile directory name containing '''+payload+''' lands on disk via any normal vector - git clone, archive extraction, npm package, downloaded zip, etc.
2. The victim has the recommended tools/quota-statusline.sh wired into their CC statusLine config.
3. The victim cds anywhere a hostile path is reachable.
4. CC fires the statusline hook on every redraw. The Python literal closes early. The injected bytes execute as Python in the user's process.

Severity

Local code execution at user privilege. Persistent re-fire on every statusline redraw. No user interaction beyond cd-ing into the hostile path. The user's shell, CC session, files, SSH keys, and any locally-accessible credentials are reachable from the executed code.

Vulnerable pattern

input=$(cat)
result=$(python3 -c "
    stdin_data = json.loads('''$input''') if '''$input''' else {}
")

Fix

Capture stdin in bash, export to env, and pipe the Python source through a single-quoted heredoc (<<'PYEOF'). Single-quoting disables ALL bash interpolation inside the body. Python reads the JSON via os.environ.get('CC_INPUT'), where the bytes are inert at every layer.

CC_INPUT=$(cat)
export CC_INPUT

python3 <<'PYEOF' 2>/dev/null
import os, json
try:
    cc_input = json.loads(os.environ.get('CC_INPUT') or '{}')
except Exception:
    cc_input = {}
# ...
PYEOF

Workarounds

Until upgrading to v3.5.2:

• Disable the statusline by removing the statusLine entry from ~/.claude/settings.json, or
• Replace tools/quota-statusline.sh with a script that does NOT pass stdin through python3 -c "..." (a heredoc + env var rewrite is safe)

Credit

Reported by Jakob Linke (@schuay) via GitHub issue #108.

Timeline

• 2026-05-07 - reported (#108)
• 2026-05-07 - confirmed, fix implemented (#110)
• 2026-05-07 - v3.5.2 published