{"id":"PYSEC-2026-2408","summary":"ciguard: discover_pipeline_files follows symlinks out of scan root","details":"## Summary\n\nThe `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.\n\n## Threat scenario\n\n**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.\n\n## Patch\n\n- New `follow_symlinks: bool = False` parameter on `discover_pipeline_files`. Default refuses to descend into symlinked directories OR symlinked files.\n- Belt-and-braces: results are filtered to those whose `.resolve()` lies under `root.resolve()`, applied even when callers opt in to `follow_symlinks=True`.\n- 3 regression tests in `tests/test_discovery.py::TestSymlinkSafety`.\n\n## Discovery\n\nFound during ciguard's first self-conducted penetration test cycle (PTES + OWASP TG v4.2 + CREST framing), 2026-04-26.\n\n## CVSS Scoring\n\n- 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)\n- 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.\n\n## Reproduction\n\n```python\nfrom pathlib import Path\nfrom ciguard.discovery import discover_pipeline_files\n# In a victim dir, plant: trojan -\u003e /etc\n# (or any other accessible dir containing pipeline-shaped files)\nfor f in discover_pipeline_files(Path('/tmp/victim')):\n    print(f)  # pre-fix: includes paths under /etc; post-fix: only /tmp/victim/\n```\n\n## References\n\n- Fix released in [v0.8.2](https://github.com/Jo-Jo98/ciguard/releases/tag/v0.8.2)\n- CI regression gate added in [v0.8.3](https://github.com/Jo-Jo98/ciguard/releases/tag/v0.8.3)\n- https://www.cve.org/CVERecord?id=CVE-2026-44220\n\nSee also: [GHSA-w828-4qhx-vxx3](https://github.com/advisories/GHSA-w828-4qhx-vxx3) — same conceptual pattern (path-validation flaw in an AI-agent tool) in Claude SDK for Python, CWE-59 + CWE-367","aliases":["CVE-2026-44220","GHSA-8cxw-cc62-q28v"],"modified":"2026-07-13T16:32:11.271630722Z","published":"2026-07-13T15:15:38.557974Z","references":[{"type":"WEB","url":"https://github.com/Jo-Jo98/ciguard/security/advisories/GHSA-8cxw-cc62-q28v"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-44220"},{"type":"PACKAGE","url":"https://github.com/Jo-Jo98/ciguard"},{"type":"WEB","url":"https://github.com/Jo-Jo98/ciguard/releases/tag/v0.8.2"},{"type":"WEB","url":"https://github.com/Jo-Jo98/ciguard/releases/tag/v0.8.3"},{"type":"PACKAGE","url":"https://pypi.org/project/ciguard"},{"type":"ADVISORY","url":"https://github.com/advisories/GHSA-8cxw-cc62-q28v"}],"affected":[{"package":{"name":"ciguard","ecosystem":"PyPI","purl":"pkg:pypi/ciguard"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0.8.0"},{"fixed":"0.8.2"}]}],"versions":["0.8.1"],"database_specific":{"source":"https://github.com/pypa/advisory-database/blob/main/vulns/ciguard/PYSEC-2026-2408.yaml"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:N"},{"type":"CVSS_V4","score":"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"}]}