CVE-2026-16158 – @fastify/reply-from vulnerable to cross-upstream request routing via URL cache key collision

CVE ID :CVE-2026-16158

Published : July 18, 2026, 1:17 p.m. | 22 minutes ago

Description :Impact: @fastify/reply-from versions from 8.3.1 up to but not including 12.6.4 build the internal URL cache key by concatenating the destination and source path without a delimiter. Different destination and source pairs can therefore produce the same key while resolving to different upstream URLs. When getUpstream selects an upstream from request data, a URL cached for one upstream can be reused for a request intended for another upstream, causing cross-upstream data access and modification. The default configuration is affected. Setting disableCache to true prevents the behavior. Patches: upgrade to @fastify/reply-from 12.6.4. Workarounds: pass disableCache: true when registering the plugin.

Severity: 8.7 | HIGH

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