Advisory details:
github_osv / GHSA-568f-pv23-39p4
| Advisory ID | github_osv/GHSA-568f-pv23-39p4 |
| Aliases |
CVE-2026-62385
|
| Summary | NLTK: Stable FrameNet and NKJP readers parse outside-root XML ### Summary Published `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. ### Details - **Vulnerability type:** Path traversal and trusted-root bypass - **Affected component:** `FramenetCorpusReader.frame_by_name`, `FramenetCorpusReader.doc`, `FramenetCorpusReader.lu`, `NKJPCorpusReader.header` - **Affected versions:** Published `3.9.4` reproduced. Current source `v3.10.0-rc2` acted as a negative control and blocked the same payloads. - **Patched versions:** Patched in version 3.10.0, which includes the path-safety rejections seen in the release candidate. - **Root cause:** Stable reader paths still construct raw XML filenames from unsafe selectors, poisoned index state, or unsafe file identifiers. I 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. ### PoC **Preconditions** - The application exposes FrameNet or NKJP reader APIs while trusting NLTK to keep XML parsing inside a corpus root. **Steps** 1. Create a minimal FrameNet or NKJP corpus root and place attacker-chosen XML files outside that root. 2. Feed unsafe selectors or poisoned index state into the relevant public stable `3.9.4` APIs. 3. Observe `frame_by_name`, `doc`, `lu(...).exemplars`, or `header` return parsed outside-root values. 4. Run the same payloads against current source and observe explicit path-safety rejections. **Minimal reproducible excerpt** ```text framenet_frame_definition FRAME_LEAK framenet_doc_text DOC_LEAK framenet_lu_text LU_LEAK nkjp_header_title HEADER_LEAK ``` ### Impact Applications 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. ### Remediation Keep 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. ### Resources - https://github.com/nltk/nltk/blob/3.9.4/nltk/corpus/reader/framenet.py#L1366-L1369 - https://github.com/nltk/nltk/blob/3.9.4/nltk/corpus/reader/framenet.py#L1456-L1460 - https://github.com/nltk/nltk/blob/3.9.4/nltk/corpus/reader/framenet.py#L1803-L1810 - https://github.com/nltk/nltk/blob/3.9.4/nltk/corpus/reader/nkjp.py#L96-L103 - https://github.com/nltk/nltk/blob/3.9.4/nltk/corpus/reader/nkjp.py#L251-L256 - https://github.com/nltk/nltk/blob/v3.10.0-rc2/nltk/corpus/reader/framenet.py#L1388-L1399 - https://github.com/nltk/nltk/blob/v3.10.0-rc2/nltk/corpus/reader/nkjp.py#L96-L128 |
| Status | Published |
| Exploitability | 0.5 |
| Weighted Severity | 7.4 |
| Risk | 3.7 |
| Affected and Fixed Packages | Package Details |
| Introduced and Fixed Package Commit Patches | Package Commit Patches Details |
| System | Score | Found at |
|---|---|---|
| cvssv3.1 | 5.9 | https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-568f-pv23-39p4/GHSA-568f-pv23-39p4.json |
| cvssv4 | 8.2 | https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-568f-pv23-39p4/GHSA-568f-pv23-39p4.json |
| generic_textual | HIGH |
No EPSS data available for this advisory.
| Patch URL | |
|---|---|
| There are no known patches. | |
| Attack Vector (AV) | Attack Complexity (AC) | Privileges Required (PR) | User Interaction (UI) | Scope (S) | Confidentiality Impact (C) | Integrity Impact (I) | Availability Impact (A) |
|---|---|---|---|---|---|---|---|
network adjacent_network local physical |
low high |
none low high |
none required |
unchanged changed |
high low none |
high low none |
high low none |
| Attack Vector (AV) | Attack Complexity (AC) | Attack Requirements (AT) | Privileges Required (PR) | User Interaction (UI) | Vulnerable System Impact Confidentiality (VC) | Vulnerable System Impact Integrity (VI) | Vulnerable System Impact Availability (VA) | Subsequent System Impact Confidentiality (SC) | Subsequent System Impact Integrity (SI) | Subsequent System Impact Availability (SA) |
|---|---|---|---|---|---|---|---|---|---|---|
network adjacent local physical |
low high |
none present |
none low high |
none passive active |
high low none |
high low none |
high low none |
high low none |
high low none |
high low none |
There are no SSVC decisions available.