{"schema":"threatline.record/2","record":{"id":"GHSA-5fqc-mrg8-w798","aliases":["CVE-2026-114097","GHSA-5fqc-mrg8-w798"],"summary":"Dulwich: Symlink directory traversal in filter-branch index_filter via cross-commit state persistence","details":"## Summary\n\nDulwich's `filter_branch.py` `CommitFilter._apply_index_filter()` is vulnerable to symlink directory traversal. When processing commit history, materialized tree entries (including symlinks) persist in the working directory between commits, allowing a symlink from an ancestor commit to redirect file writes from a descendant commit to arbitrary filesystem locations.\n\n## Root Cause\n\n`_apply_index_filter()` at `dulwich/filter_branch.py:212` calls `build_index_from_tree(\".\", tmp_index_path, ...)` which materializes all tree entries to the current working directory. The `finally` block (line 229-230) only cleans up the temporary index file (`os.unlink(tmp_index_path)`) — NOT the filesystem files written to CWD. When `process_commit()` processes parents recursively first (line 260), files materialized from ancestor commits persist and affect processing of descendant commits.\n\nOn dulwich 1.2.7, `build_file_from_blob()` has no symlink protection, and `validate_path_element` only validates name patterns, not filesystem state.\n\n## Impact\n\nAn attacker can craft a malicious repository where running `filter_branch` with an index filter writes attacker-controlled content to arbitrary filesystem locations via symlink traversal. This achieves RCE if the write targets `.git/hooks/`.\n\n## Attack Scenario\n\n1. Attacker creates a repository where commit history (linearized) has:\n   - Ancestor commit: tree entry `evil` (mode 120000, symlink → `/target_dir`)\n   - Descendant commit: tree entry `evil/payload` (mode 100644, attacker content)\n2. Victim clones repository and runs `filter_branch` with an index filter\n3. `process_commit()` processes ancestor first → materializes `evil` as symlink to `/target_dir` in CWD\n4. CWD is NOT cleaned between commits\n5. Processing descendant: `os.path.exists(\"./evil\")` → True (symlink exists). `build_file_from_blob(blob, mode, \"./evil/payload\")` → `open(\"./evil/payload\", \"wb\")` follows intermediate symlink → writes to `/target_dir/payload`\n\n## Suggested Fix\n\nClean the CWD between commit iterations in `_apply_index_filter()`, or verify that no intermediate path components are symlinks before writing files.\n\nReported by **zx (Jace)**","categories":["Libraries & packages"],"product":"dulwich","vendor":"","ecosystem":"pip","affected_ranges":[{"source":"GitHub Advisory Database","source_url":"https://github.com/advisories/GHSA-5fqc-mrg8-w798","source_modified_at":"2026-10-02T18:53:05Z","fetched_at":"2026-10-23T18:42:43.628194Z","package":{"ecosystem":"pip","name":"dulwich"},"range":">= 0.23.1, <= 1.2.7"},{"source":"OSV","source_url":"https://osv.dev/vulnerability/GHSA-5fqc-mrg8-w798","source_modified_at":"2026-10-21T10:57:27.569314986Z","fetched_at":"2026-10-23T18:42:43.628194Z","package":{"name":"dulwich","ecosystem":"PyPI","purl":"pkg:pypi/dulwich"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0.23.1"},{"fixed":"1.2.8"}]}],"versions":["0.23.1","0.23.2","0.24.0","0.24.1","0.24.10","0.24.2","0.24.3","0.24.4","0.24.5","0.24.6","0.24.7","0.24.8","0.24.9","0.25.0","0.25.1","0.25.2","1.0.0","1.1.0","1.2.0","1.2.1","1.2.2","1.2.3","1.2.4","1.2.5","1.2.6","1.2.7"]}],"fixed_versions":[{"source":"GitHub Advisory Database","source_url":"https://github.com/advisories/GHSA-5fqc-mrg8-w798","source_modified_at":"2026-10-02T18:53:05Z","fetched_at":"2026-10-23T18:42:43.628194Z","package":{"ecosystem":"pip","name":"dulwich"},"version":"1.2.8"},{"source":"OSV","source_url":"https://osv.dev/vulnerability/GHSA-5fqc-mrg8-w798","source_modified_at":"2026-10-21T10:57:27.569314986Z","fetched_at":"2026-10-23T18:42:43.628194Z","package":{"name":"dulwich","ecosystem":"PyPI","purl":"pkg:pypi/dulwich"},"version":"1.2.8"}],"cvss":8.6,"severity":"High","kev":{"listed":false},"epss":{"probability":null,"percentile":null,"score_date":null},"published_at":"2026-10-02T18:53:05Z","modified_at":"2026-10-21T10:57:27.569314986Z","provenance":[{"source":"GitHub Advisory Database","url":"https://github.com/advisories/GHSA-5fqc-mrg8-w798","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-02T18:53:05Z"},{"source":"OSV","url":"https://osv.dev/vulnerability/GHSA-5fqc-mrg8-w798","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-21T10:57:27.569314986Z"}],"sources":["GitHub Advisory Database","OSV"],"references":[{"url":"https://github.com/jelmer/dulwich/security/advisories/GHSA-5fqc-mrg8-w798","source":"GitHub Advisory Database"},{"url":"https://github.com/jelmer/dulwich/commit/9571ac60b851fce228dae7ededb380c6ce9b3fb8","source":"GitHub Advisory Database"},{"url":"https://github.com/jelmer/dulwich/releases/tag/dulwich-1.2.8","source":"GitHub Advisory Database"},{"url":"https://github.com/advisories/GHSA-5fqc-mrg8-w798","source":"GitHub Advisory Database"}],"locations":[],"motoko_assessment":{"status":"requires_architecture_review","automatic_remediation":false},"classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":"ecosystem","confidence":"heuristic","reviewed":false},"change_timestamp":"2026-10-21T10:57:27.569314986Z","content_hash":"e8b0911510e432cd5f622ef320a831dbe1ab5e5c4b333755a5f0af6cff816011"}}