CVE-2026-16158

Summary

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.

Affected Software

VendorProductVersion RangeStatus
@fastify/reply-from@fastify/reply-from8.3.1 < 12.6.4affected
@fastify/reply-from@fastify/reply-from12.6.4unaffected

Weaknesses

  • CWE-441: CWE-441: Unintended Proxy or Intermediary ('Confused Deputy')

References