PatchTheCVECVE-2026-15631: Impact: @fastify/http-proxy versions from 9.4.0 up to and including 11.5.0 fail to validate the resolved WebSo
CVE-2026-15631 is a high-severity flaw (CVSS 8.7) affecting fastify\/http-proxy. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
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 me
Why this priority
- High severity
- Remotely exploitable, no login, no user action
A fixed release or distro patch exists.
Risk facts
| CVSS score | 8.7 (High) |
| Attack vector | Network (remote) |
| Attack complexity | High |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 0.5% (top 57%) |
| CISA exploited list | No |
| Weakness | CWE-22 |
| Published | 2026-07-18 |
| Last modified | 2026-07-28 |
Last updated 2026-07-28 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2026-15631?
fastify\/http-proxy: upgrade to 11.6.0. Exact commands for each OS are on this page.
Is CVE-2026-15631 being exploited?
CVE-2026-15631 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2026-15631 affect?
CVE-2026-15631 affects fastify\/http-proxy. Severity is high (CVSS 8.7). 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 th
How urgent is CVE-2026-15631?
Priority 46/100. High severity; Remotely exploitable, no login, no user action
Related CVEs
- CVE-2026-33805 HIGH 8.6 UPGRADE UPGRADE @fastify/reply-from v12.6.1 and earlier and @fastify/http-proxy v11.4.3 and earlier process the client's Conne
- CVE-2026-85124 HIGH 7.5 UPGRADE @fastify/http-proxy versions before 11.6.2 do not validate proxied HTTP request paths for backslash based dot-
- CVE-2026-16117 CRITICAL 10.0 UPGRADE Impact: @fastify/http-proxy versions up to and including 11.5.0 fail to rewrite the request prefix when the pr