GHSA-8cxw-cc62-q28v ciguard: discover_pipeline_files follows symlinks out of scan root

• PyPI ciguard: >= 0.8.0, < 0.8.2 → fixed in 0.8.2

Summary The `discover_pipeline_files()` function in `src/ciguard/discovery.py` (introduced in v0.8.0 and used by the MCP `scan_repo` tool shipped in v0.8.1) walks a directory tree following symlinks, with cycle protection via tracking visited resolved paths. An attacker who can plant a symlink in a directory the user (or AI agent) scans can cause discovery to walk into the symlink target and return paths to pipeline-shaped files outside the requested root. Threat scenario MCP confused-deputy. A user runs Claude Desktop / Claude Code / Cursor with the ciguard MCP server registered. The agent is fed an adversarial prompt to scan a directory containing planted symlinks (e.g. via a malicious clone or extracted tarball). `ciguard.scan_repo` walks the symlinks, returning paths and (via subsequent `scan` calls) file content from `~/.aws/`, `~/.config/`, `/etc/some-pipeline-config/`, etc. Pipeline files often contain hardcoded secrets, internal hostnames, deploy keys. Patch • New `follow_symlinks: bool = False` parameter on `discover_pipeline_files`. Default refuses to descend into symlinked directories OR symlinked files. • Belt-and-braces: results are filtered to those whose `.resolve()` lies under `root.resolve()`, applied even when callers opt in to `follow_symlinks=True`. • 3 regression tests in `tests/test_discovery.py::TestSymlinkSafety`. Discovery Found during ciguard's first self-conducted penetration test cycle (PTES + OWASP TG v4.2 + CREST framing), 2026-04-26. CVSS Scoring • CVSS v3.1: `CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:L/I:N/A:N` — 4.4 (Medium) • CVSS v4.0: `CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:P/VC:L/VI:N/VA:N/SC:L/SI:N/SA:N` — first.org calc 5.7 (Medium); GitHub's calc returns 2.4 (Low). Vector is correct — calculator profiles differ. Reproduction ```python from pathlib import Path from ciguard.discovery import discover_pipeline_files In a victim dir, plant: trojan -> /etc (or any other accessible dir containing pipeline-shaped files) for f in discover_pipeline_files(Path('/tmp/victim')): print(f) # pre-fix: includes paths under /etc; post-fix: only /tmp/victim/ ``` References • Fix released in v0.8.2 • CI regression gate added in v0.8.3 • https://www.cve.org/CVERecord?id=CVE-2026-44220 See also: GHSA-w828-4qhx-vxx3 — same conceptual pattern (path-validation flaw in an AI-agent tool) in Claude SDK for Python, CWE-59 + CWE-367