Reference page — cumulative record through Wednesday, August 19, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.
AV AC PR UI S C I A CVSS EPSS %ile KEV N L N N C H H N 10.0 .0033 25.6 —
AFFECTED Product Versions Fixed @fastify/http-proxy 9.4.0 – 11.6.0
TIMELINE Jul 13 Reserved by openjs Jul 18 Published (CNA: openjs) Jul 28 RESCORED — CVE-2026-15631 (@fastify/http-proxy). CVSS 8.7 → 10 (NVD).
Impact: @fastify/http-proxy versions from 9.4.0 up to and including 11.5.0 fail to validate the resolved WebSocket destination path against the configured rewrite prefix. The WebSocket routing path in WebSocketProxy.findUpstream resolves the destination via the WHATWG URL constructor, which collapses dot segments, so a crafted upgrade request with path traversal sequences can escape the rewrite prefix and reach upstream endpoints that were not meant to be exposed by the proxy. This is a variant of CVE-2021-21322 in a code path that never went through the HTTP fix in fastify/reply-from. Exploitation requires a non-normalizing WebSocket client, since browsers and the ws package normalize the request path before sending, but raw HTTP clients or downstream proxies that forward the request target unchanged make the attack reachable in production topologies. Patches: upgrade to @fastify/http-proxy 11.6.0. Workarounds: none.
| Date | Event | Detail |
|---|---|---|
| July 13, 2026 | Reserved | Reserved by openjs |
| July 18, 2026 | Published | Published (CNA: openjs) |
| July 28, 2026 | RESCORED | RESCORED — CVE-2026-15631 (@fastify/http-proxy). CVSS 8.7 → 10 (NVD). |
| Vendor | Product / Package | Ecosystem | Version introduced | Fixed |
|---|---|---|---|---|
| @fastify/http-proxy | @fastify/http-proxy | — | 9.4.0 | 11.6.0 |
Authoritative record: CVE-2026-15631 at cve.org
Vendors: @fastify/http-proxy
Weaknesses: CWE-22
This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-15631 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Wednesday, August 19, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.