{"items":[{"id":"NVI-00013807","kind":"vulnerability","title":"NLTK: Pl196xCorpusReader has quadratic ReDoS on malformed TEI blocks","revision":1,"unknowns":["Customer inventory, deployment, reachability and exploitation have not been inspected."],"lifecycle":"active","identifiers":["GHSA-8mpw-7fpc-4gqj","CVE-2026-81725"],"plain_summary":"GitHub lists this reviewed advisory for nltk. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.","review_status":"source_listed","control_topics":[],"public_actions":[{"summary":"Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.","source_ids":["sr-086efdf15fcdc64dd8a52a18c34d37d0"],"action_type":"investigate","limitations":"Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system.","current_supported_target":null}],"schema_version":"1.1.0","source_metrics":[],"why_it_matters":"Published affected context helps an owner decide what evidence to gather. This report has not examined your application.","related_sources":[{"id":"sr-086efdf15fcdc64dd8a52a18c34d37d0","url":"https://github.com/advisories/GHSA-8mpw-7fpc-4gqj","basis":"vendor_advisory","notes":"GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.","title":"GHSA-8mpw-7fpc-4gqj","publisher":"GitHub Advisory Database","observed_at":"2026-11-02T02:20:31.767Z"}],"affected_context":[{"certainty":"source_listed","source_ids":["sr-086efdf15fcdc64dd8a52a18c34d37d0"],"technology":"nltk","known_exclusions":[],"conditions_summary":"### Summary\n\n`Pl196xCorpusReader` still parses whole TEI blocks with multiple lazy regexes over attacker-controlled text. A malformed file with many opening tags and no matching closing tags forces repeated rescans and produces quadratic CPU growth in public reader APIs.\n\n### Details\n\n- **Vulnerability type:** Regular-expression denial of service\n- **Affected component:** `nltk.corpus.reader.pl196x.TEICorpusView.read_block` and `Pl196xCorpusReader` public methods\n- **Affected versions:** Published `3.9.4` and current source `v3.10.0-rc2` both reproduced.\n- **Patched versions:** Not yet patched\n- **Root cause:** Lazy `.*?` whole-block regexes rescan untrusted XML-like blocks from each opening-tag position.\n\nThe parser uses regexes for paragraphs, sentences, and word tags across the whole `` block. When the attacker supplies many unmatched opening tags, each attempt scans toward the end of the block and fails, then restarts from the next opening tag. There is near four-times runtime growth each time the number of malformed `` tags doubled, through normal public calls such as `words()` and `tagged_words()`.\n\n### PoC\n\n**Preconditions**\n- The application parses attacker-influen","public_affected_ranges":["<= 3.10.2"]}],"null_published_at":"2026-11-02T10:00:37.153Z","source_updated_at":"2026-09-08T20:28:47.000Z","source_disclosed_at":"2026-09-08T20:28:46.000Z","is_synthetic_fixture":false,"null_last_reviewed_at":null,"public_change_summary":"First indexed by Null; source disclosure date is shown separately.","null_first_observed_at":"2026-11-02T02:20:31.767Z"}],"next_cursor":null,"snapshot_revision":"42594"}