{"items":[{"id":"NVI-00018580","kind":"vulnerability","title":"Bleach clean() / Cleaner() fails to sanitize dangerous URI schemes in allowed formaction attributes","revision":1,"unknowns":["Customer inventory, deployment, reachability and exploitation have not been inspected."],"lifecycle":"active","identifiers":["GHSA-gj48-438w-jh9v"],"plain_summary":"GitHub lists this reviewed advisory for bleach. 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-3f5a3152671a5c693c4a6d4033c6f176"],"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":[{"kind":"CVSS","as_of":"2026-06-16T14:07:50.000Z","value":"6.1 medium","meaning":"GitHub source severity; exploitability and local consequence require separate evidence.","source_id":"sr-3f5a3152671a5c693c4a6d4033c6f176"}],"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-3f5a3152671a5c693c4a6d4033c6f176","url":"https://github.com/advisories/GHSA-gj48-438w-jh9v","basis":"vendor_advisory","notes":"GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.","title":"GHSA-gj48-438w-jh9v","publisher":"GitHub Advisory Database","observed_at":"2026-11-06T07:20:20.042Z"}],"affected_context":[{"certainty":"source_listed","source_ids":["sr-3f5a3152671a5c693c4a6d4033c6f176"],"technology":"bleach","known_exclusions":[],"conditions_summary":"### Summary\n\nBleach `clean()` / `Cleaner()` fails to sanitize dangerous URI schemes in allowed `formaction` attributes.\n\nBleach applies URI protocol sanitization only to attributes listed in `attr_val_is_uri`. While URI-bearing attributes such as `action`, `href`, `src`, and `poster` are included in that set, `formaction` is not. As a result, if a downstream application explicitly allows `formaction` on submit-capable controls in untrusted HTML, Bleach preserves dangerous values such as `javascript:alert(1)` instead of stripping them.\n\nThis can lead to **submit-triggered JavaScript execution** in applications that rely on Bleach to sanitize untrusted HTML and allow the relevant tag/attribute combination.\n\n---\n\n### Details\n\nThe issue appears to be a URI-sanitization coverage gap in Bleach’s sanitizer logic.\n\nRelevant code paths:\n\n* `bleach/sanitizer.py` — `BleachSanitizerFilter.allow_token` (around line 553)\n* `bleach/_vendor/html5lib/filters/sanitizer.py` — `attr_val_is_uri` (around line 525)\n\nIn `BleachSanitizerFilter.allow_token`, URI protocol sanitization is only applied when:\n\n```python id=\"pft79m\"\nif namespaced_name in self.attr_val_is_uri:\n```\n\nHowever, `(None, 'formaction')`","public_affected_ranges":["< 6.4.0"]}],"null_published_at":"2026-11-07T07:07:39.858Z","source_updated_at":"2026-06-16T14:07:50.000Z","source_disclosed_at":"2026-06-16T14:07:49.000Z","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":"2026-11-06T07:20:20.042Z"}],"next_cursor":null,"snapshot_revision":"42594"}