Fiber: CORS wildcard origins matched without a dot boundary, allowing credentialed cross-origin reads

[ Why it matters ]Priority signals

• Public proof-of-concept exploit exists (CISA SSVC)

[ Description ]Official description

Fiber is an Express inspired web framework written in Go. From 2.52.1 until 2.52.3, the CORS middleware's validateDomain wildcard matcher in middleware/cors/utils.go strips the scheme and checks only a host suffix without requiring a dot boundary. An application configured with a wildcard-subdomain AllowOrigins value and AllowCredentials enabled can reflect an unrelated attacker-controlled origin whose host merely ends with the configured base domain. A user who visits that origin can expose authenticated cross-origin responses to the attacker's page; empty-label origins and later comma-space parsing hardening are outside this advisory. This issue is fixed in version 2.52.3.

[ Fixes ]Fixes and patches

• github.com/gofiber/fiber/v2 2.52.3Fixed version · GitHub Advisories · go package github.com/gofiber/fiber/v2: upgrade to 2.52.3 or later (affected >= 2.52.1, <= 2.52.2)

[ Packages ]Affected open-source packages

• github.com/gofiber/fiber/v2 goAffected >= 2.52.1, <= 2.52.2 · fixed in 2.52.3 · GHSA-g5jq-qmqr-qrwf

[ References ]References

• github.com/gofiber/fiber/commit/1aac6f618b6bd3e159d2449acb4232a2170b976b
• github.com/gofiber/fiber/pull/2915
• github.com/gofiber/fiber/releases/tag/v2.52.3
• github.com/gofiber/fiber/security/advisories/GHSA-g5jq-qmqr-qrwf