{"id":"GHSA-568f-pv23-39p4","summary":"NLTK: Stable FrameNet and NKJP readers parse outside-root XML","details":"### Summary\n\nPublished `nltk==3.9.4` still contains several XML-reader entrypoints that build parser paths from caller-controlled selectors or trusted-looking index state without preserving the corpus-root boundary.\n\n### Details\n\n- **Vulnerability type:** Path traversal and trusted-root bypass\n- **Affected component:** `FramenetCorpusReader.frame_by_name`, `FramenetCorpusReader.doc`, `FramenetCorpusReader.lu`, `NKJPCorpusReader.header`\n- **Affected versions:** Published `3.9.4` reproduced. Current source `v3.10.0-rc2` acted as a negative control and blocked the same payloads.\n- **Patched versions:** Patched in version 3.10.0, which includes the path-safety rejections seen in the release candidate.\n- **Root cause:** Stable reader paths still construct raw XML filenames from unsafe selectors, poisoned index state, or unsafe file identifiers.\n\nI confirmed four public stable entrypoints return parsed outside-root content: a parent-segment traversal frame name, a poisoned fulltext index filename, a poisoned LU id, and an unsafe NKJP header file identifier. Current source rejects the same payloads with explicit path-safety errors, which shows the bug is real but version-scoped to the published stable package.\n\n### PoC\n\n**Preconditions**\n- The application exposes FrameNet or NKJP reader APIs while trusting NLTK to keep XML parsing inside a corpus root.\n\n**Steps**\n1. Create a minimal FrameNet or NKJP corpus root and place attacker-chosen XML files outside that root.\n2. Feed unsafe selectors or poisoned index state into the relevant public stable `3.9.4` APIs.\n3. Observe `frame_by_name`, `doc`, `lu(...).exemplars`, or `header` return parsed outside-root values.\n4. Run the same payloads against current source and observe explicit path-safety rejections.\n\n**Minimal reproducible excerpt**\n\n```text\nframenet_frame_definition FRAME_LEAK\nframenet_doc_text DOC_LEAK\nframenet_lu_text LU_LEAK\nnkjp_header_title HEADER_LEAK\n```\n\n### Impact\n\nApplications that process attacker-influenced FrameNet or NKJP corpus selectors or state can be made to parse XML outside the trusted corpus root through normal public reader responses.\n\n### Remediation\n\nKeep these reader paths on the same root-confinement model as `CorpusReader.open()` and `nltk.pathsec`. Reject unsafe path components before constructing filenames from frame names, document filenames, LU ids, or NKJP file identifiers.\n\n### Resources\n\n- https://github.com/nltk/nltk/blob/3.9.4/nltk/corpus/reader/framenet.py#L1366-L1369\n- https://github.com/nltk/nltk/blob/3.9.4/nltk/corpus/reader/framenet.py#L1456-L1460\n- https://github.com/nltk/nltk/blob/3.9.4/nltk/corpus/reader/framenet.py#L1803-L1810\n- https://github.com/nltk/nltk/blob/3.9.4/nltk/corpus/reader/nkjp.py#L96-L103\n- https://github.com/nltk/nltk/blob/3.9.4/nltk/corpus/reader/nkjp.py#L251-L256\n- https://github.com/nltk/nltk/blob/v3.10.0-rc2/nltk/corpus/reader/framenet.py#L1388-L1399\n- https://github.com/nltk/nltk/blob/v3.10.0-rc2/nltk/corpus/reader/nkjp.py#L96-L128","aliases":["CVE-2026-62385","PYSEC-2026-3728"],"modified":"2026-09-08T16:45:03.600943920Z","published":"2026-09-08T16:37:18Z","database_specific":{"severity":"HIGH","github_reviewed":true,"github_reviewed_at":"2026-09-08T16:37:18Z","nvd_published_at":null,"cwe_ids":["CWE-22","CWE-706","CWE-73"]},"references":[{"type":"WEB","url":"https://github.com/nltk/nltk/security/advisories/GHSA-568f-pv23-39p4"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-62385"},{"type":"WEB","url":"https://github.com/nltk/nltk/pull/3579"},{"type":"WEB","url":"https://github.com/nltk/nltk/pull/3581"},{"type":"WEB","url":"https://github.com/nltk/nltk/commit/7d1389d0789c1eca56bd0ed444089e0a3972e3ed"},{"type":"WEB","url":"https://github.com/nltk/nltk/commit/bf3bf32786791394a1008258b4917a7f2d4dbcda"},{"type":"PACKAGE","url":"https://github.com/nltk/nltk"},{"type":"WEB","url":"https://github.com/nltk/nltk/releases/tag/v3.10.0"},{"type":"WEB","url":"https://github.com/pypa/advisory-database/tree/main/vulns/nltk/PYSEC-2026-3728.yaml"},{"type":"WEB","url":"https://www.vulncheck.com/advisories/nltk-path-traversal-via-framenet-and-nkjp-readers"}],"affected":[{"package":{"name":"nltk","ecosystem":"PyPI","purl":"pkg:pypi/nltk"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.10.0"}]}],"versions":["0.8","0.9","0.9.3","0.9.4","0.9.5","0.9.6","0.9.7","0.9.8","0.9.9","2.0.1","2.0.1rc1","2.0.1rc2-git","2.0.1rc3","2.0.1rc4","2.0.2","2.0.3","2.0.4","2.0.5","2.0b4","2.0b5","2.0b6","2.0b7","2.0b8","2.0b9","3.0.0","3.0.0b1","3.0.0b2","3.0.1","3.0.2","3.0.3","3.0.4","3.0.5","3.1","3.2","3.2.1","3.2.2","3.2.3","3.2.4","3.2.5","3.3","3.4","3.4.1","3.4.2","3.4.3","3.4.4","3.4.5","3.5","3.5b1","3.6","3.6.1","3.6.2","3.6.3","3.6.4","3.6.5","3.6.6","3.6.7","3.7","3.8","3.8.1","3.9","3.9.1","3.9.2","3.9.3","3.9.4","3.9b1"],"database_specific":{"last_known_affected_version_range":"\u003c= 3.9.4","source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-568f-pv23-39p4/GHSA-568f-pv23-39p4.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N"},{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N"}]}