{"items":[{"id":"NVI-00018623","kind":"vulnerability","title":"undici vulnerable to Set-Cookie SameSite attribute downgrade via permissive substring matching","revision":1,"unknowns":["Customer inventory, deployment, reachability and exploitation have not been inspected."],"lifecycle":"active","identifiers":["GHSA-g8m3-5g58-fq7m","CVE-2026-11525"],"plain_summary":"GitHub lists this reviewed advisory for undici, undici, undici. 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-458897a4cc7ababffc72bc59bb75a804"],"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":"2026-06-19T14:34:46.000Z","value":"3.7 low","meaning":"GitHub source severity; exploitability and local consequence require separate evidence.","source_id":"sr-458897a4cc7ababffc72bc59bb75a804"}],"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-458897a4cc7ababffc72bc59bb75a804","url":"https://github.com/advisories/GHSA-g8m3-5g58-fq7m","basis":"vendor_advisory","notes":"GitHub Advisory Database; CC-BY-4.0. Each advisory links its original attribution. Null normalizes fields.","title":"GHSA-g8m3-5g58-fq7m","publisher":"GitHub Advisory Database","observed_at":"2026-11-06T07:19:16.585Z"}],"affected_context":[{"certainty":"source_listed","source_ids":["sr-458897a4cc7ababffc72bc59bb75a804"],"technology":"undici","known_exclusions":[],"conditions_summary":"## Impact\n\nWhen undici parses a `Set-Cookie` header, it accepts any `SameSite` attribute value that contains `Strict`, `Lax`, or `None` as a substring, rather than the case-insensitive exact match specified by RFC 6265. Non-spec values are silently mapped to one of the three standard tokens:\n\n- `SameSite=NoneOfYourBusiness` is parsed as `None`, the most permissive setting.\n- `SameSite=StrictLax` is parsed as `Lax`, a downgrade from `Strict`.\n\nAffected applications are those that consume `Set-Cookie` headers from server responses (for example via undici's `fetch` or proxy code paths) and then forward or rely on the parsed `sameSite` attribute. A malicious or non-compliant server can coerce the consumer's view of a cookie's SameSite policy to a weaker value, silently degrading the SameSite enforcement the cookie is supposed to provide.\n\nThis was introduced in undici 5.15.0 when the cookies feature was added.\n\n## Patches\n\nUpgrade to undici v6.27.0, v7.28.0 or v8.5.0.\n\n## Workarounds\n\nAfter parsing a `Set-Cookie` header, validate that the resulting `sameSite` attribute is one of `'Strict'`, `'Lax'`, or `'None'` (exact, case-insensitive) before forwarding or relying on it.","public_affected_ranges":["< 6.27.0"]},{"certainty":"source_listed","source_ids":["sr-458897a4cc7ababffc72bc59bb75a804"],"technology":"undici","known_exclusions":[],"conditions_summary":"## Impact\n\nWhen undici parses a `Set-Cookie` header, it accepts any `SameSite` attribute value that contains `Strict`, `Lax`, or `None` as a substring, rather than the case-insensitive exact match specified by RFC 6265. Non-spec values are silently mapped to one of the three standard tokens:\n\n- `SameSite=NoneOfYourBusiness` is parsed as `None`, the most permissive setting.\n- `SameSite=StrictLax` is parsed as `Lax`, a downgrade from `Strict`.\n\nAffected applications are those that consume `Set-Cookie` headers from server responses (for example via undici's `fetch` or proxy code paths) and then forward or rely on the parsed `sameSite` attribute. A malicious or non-compliant server can coerce the consumer's view of a cookie's SameSite policy to a weaker value, silently degrading the SameSite enforcement the cookie is supposed to provide.\n\nThis was introduced in undici 5.15.0 when the cookies feature was added.\n\n## Patches\n\nUpgrade to undici v6.27.0, v7.28.0 or v8.5.0.\n\n## Workarounds\n\nAfter parsing a `Set-Cookie` header, validate that the resulting `sameSite` attribute is one of `'Strict'`, `'Lax'`, or `'None'` (exact, case-insensitive) before forwarding or relying on it.","public_affected_ranges":[">= 7.0.0, < 7.28.0"]},{"certainty":"source_listed","source_ids":["sr-458897a4cc7ababffc72bc59bb75a804"],"technology":"undici","known_exclusions":[],"conditions_summary":"## Impact\n\nWhen undici parses a `Set-Cookie` header, it accepts any `SameSite` attribute value that contains `Strict`, `Lax`, or `None` as a substring, rather than the case-insensitive exact match specified by RFC 6265. Non-spec values are silently mapped to one of the three standard tokens:\n\n- `SameSite=NoneOfYourBusiness` is parsed as `None`, the most permissive setting.\n- `SameSite=StrictLax` is parsed as `Lax`, a downgrade from `Strict`.\n\nAffected applications are those that consume `Set-Cookie` headers from server responses (for example via undici's `fetch` or proxy code paths) and then forward or rely on the parsed `sameSite` attribute. A malicious or non-compliant server can coerce the consumer's view of a cookie's SameSite policy to a weaker value, silently degrading the SameSite enforcement the cookie is supposed to provide.\n\nThis was introduced in undici 5.15.0 when the cookies feature was added.\n\n## Patches\n\nUpgrade to undici v6.27.0, v7.28.0 or v8.5.0.\n\n## Workarounds\n\nAfter parsing a `Set-Cookie` header, validate that the resulting `sameSite` attribute is one of `'Strict'`, `'Lax'`, or `'None'` (exact, case-insensitive) before forwarding or relying on it.","public_affected_ranges":[">= 8.0.0, < 8.5.0"]}],"null_published_at":"2026-11-07T07:07:39.864Z","source_updated_at":"2026-06-19T14:34:46.000Z","source_disclosed_at":"2026-06-19T14:34:46.000Z","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":"2026-11-06T07:19:16.585Z"}],"next_cursor":null,"snapshot_revision":"42594"}