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.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
High
Difficult to exploit
Privileges Required
None
No privileges needed
User Interaction
Required
User action required
Impact Assessment
Confidentiality
High
Complete data leak
Integrity
Low
Partial data modification
Availability
None
No disruption
CVSS Vector v3.1
Weakness Type (CWE)
References 4
https://github.com/gofiber/fiber/commit/1aac6f618b6bd3e159d2449acb4232a2170b976b
security-advisories@github.com
https://github.com/gofiber/fiber/pull/2915
security-advisories@github.com
https://github.com/gofiber/fiber/releases/tag/v2.52.3
security-advisories@github.com
https://github.com/gofiber/fiber/security/advisories/GHSA-g5jq-qmqr-qrwf
security-advisories@github.com