{"schema":"threatline.record/2","record":{"id":"CVE-2026-107832","aliases":["GHSA-389g-gv7q-r4x8"],"summary":"fastify is vulnerable to header validation bypass via case-sensitive propertyNames","details":"### Impact\n\nFastify lowercases header names in a `headers` schema before compilation, because Node.js stores request header names in lowercase. This normalization does not reach the header names held in a `propertyNames` subschema's `enum` and `const`. A header-name deny-list written in the canonical header case, such as `propertyNames: { not: { enum: ['X-Debug-Override'] } }`, therefore never matches the lowercased request headers, and the forbidden header reaches the handler. Any application that uses a `propertyNames` deny-list or allow-list to constrain request header names does not get the constraint it expects. The same rule written in lowercase works, and the `not: { required: [...] }` form is unaffected, so this is a gap in the built-in normalization rather than a wrong schema. This is an incomplete fix of CVE-2026-84428 ([GHSA-9q9j-q6p8-xq58](https://github.com/fastify/fastify/security/advisories/GHSA-9q9j-q6p8-xq58)), whose normalization covered header names used as property keys but not those used as values inside `propertyNames`.\n\n### Patches\n\nUsers should upgrade to fastify `5.12.6` or later, which lowercases header names held in `enum` and `const` inside a `propertyNames` subschema so they match the lowercased request headers. Header-name constraints that cannot be normalized automatically, regular expressions (`propertyNames` `pattern` and `patternProperties` keys) and a `$ref` used inside `propertyNames`, are documented and, for the `$ref` case, warned at startup (`FSTSEC003`). Author those to match the lowercased request headers.\n\n### Workarounds\n\nWrite the `propertyNames` header-name constraint in lowercase (for example `enum: ['x-debug-override']`), or enforce the header check in an `onRequest` or `preValidation` hook instead of the schema.","categories":["Frameworks"],"product":"fastify","vendor":"fastify","ecosystem":"npm","affected_ranges":[{"source":"GitHub Advisory Database","source_url":"https://github.com/advisories/GHSA-389g-gv7q-r4x8","source_modified_at":"2026-10-22T16:40:37Z","fetched_at":"2026-10-23T18:42:43.628194Z","package":{"ecosystem":"npm","name":"fastify"},"range":">= 5.12.2, < 5.12.6"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-107832","source_modified_at":"2026-10-15T19:14:58.255Z","fetched_at":"2026-10-23T18:45:31.882637Z","product":"fastify","vendor":"fastify","versions":[{"versionType":"semver","status":"affected","version":"5.12.2","lessThan":"5.12.6"},{"versionType":"semver","status":"unaffected","version":"5.12.6"}],"defaultStatus":"unaffected"},{"source":"OSV","source_url":"https://osv.dev/vulnerability/GHSA-389g-gv7q-r4x8","source_modified_at":"2026-10-22T16:45:04.287484964Z","fetched_at":"2026-10-23T18:42:43.628194Z","package":{"ecosystem":"npm","name":"fastify","purl":"pkg:npm/fastify"},"ranges":[{"events":[{"introduced":"5.12.2"},{"fixed":"5.12.6"}],"type":"SEMVER"}],"versions":[]}],"fixed_versions":[{"source":"GitHub Advisory Database","source_url":"https://github.com/advisories/GHSA-389g-gv7q-r4x8","source_modified_at":"2026-10-22T16:40:37Z","fetched_at":"2026-10-23T18:42:43.628194Z","package":{"ecosystem":"npm","name":"fastify"},"version":"5.12.6"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-107832","source_modified_at":"2026-10-15T19:14:58.255Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"fastify","ecosystem":null},"version":"5.12.6","basis":"first unaffected version stated in the CVE record"},{"source":"OSV","source_url":"https://osv.dev/vulnerability/GHSA-389g-gv7q-r4x8","source_modified_at":"2026-10-22T16:45:04.287484964Z","fetched_at":"2026-10-23T18:42:43.628194Z","package":{"ecosystem":"npm","name":"fastify","purl":"pkg:npm/fastify"},"version":"5.12.6"}],"cvss":3.7,"severity":"Low","kev":{"listed":false},"epss":{"probability":0.00257,"percentile":0.16446,"score_date":"2026-10-23"},"published_at":"2026-10-13T13:23:24.217Z","modified_at":"2026-10-22T16:45:04.287484964Z","provenance":[{"source":"GitHub Advisory Database","url":"https://github.com/advisories/GHSA-389g-gv7q-r4x8","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-22T16:40:37Z"},{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-107832","fetched_at":"2026-10-23T18:45:31.882637Z","source_modified_at":"2026-10-15T19:14:58.255Z"},{"source":"OSV","url":"https://osv.dev/vulnerability/GHSA-389g-gv7q-r4x8","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-22T16:45:04.287484964Z"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-107832","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-23"}],"sources":["GitHub Advisory Database","CVE List","OSV","EPSS"],"references":[{"source":"CVE List","url":"https://github.com/fastify/fastify/security/advisories/GHSA-389g-gv7q-r4x8"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-107832","source":"GitHub Advisory Database"},{"url":"https://github.com/fastify/fastify/pull/7104","source":"GitHub Advisory Database"},{"url":"https://github.com/fastify/fastify/commit/3241fbd2f10a8ca1503533726836b53b6e8775a2","source":"GitHub Advisory Database"},{"url":"https://github.com/fastify/fastify/commit/35c32375731c111439682b2f9e6e0baed2694269","source":"GitHub Advisory Database"},{"source":"CVE List","url":"https://cna.openjsf.org/security-advisories.html"},{"url":"https://github.com/fastify/fastify/releases/tag/v5.12.6","source":"GitHub Advisory Database"},{"url":"https://github.com/advisories/GHSA-389g-gv7q-r4x8","source":"GitHub Advisory Database"}],"locations":[],"motoko_assessment":{"status":"requires_architecture_review","automatic_remediation":false},"cve_state":"PUBLISHED","ssvc":{"exploitation":"none","automatable":"no","technical_impact":"partial","assessed_at":"2026-10-15T17:34:08.435956Z"},"classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":"product","confidence":"heuristic","reviewed":false},"change_timestamp":"2026-10-22T16:45:04.287484964Z","content_hash":"b0ebd566a140a67ccb7261aafcaf3d91752a17905607ff810232a6df6eff3b14"}}