CVE-2026-119285: Fiber: CORS wildcard origins matched without a dot boundary, allowing credentialed cross-origin reads

Vulnerability summary

CVE-2026-119285 is a medium (CVSS 5.9) Origin Validation Error vulnerability in gofiber fiber. EPSS estimates a 0.13% chance of exploitation in the next 30 days, higher than 2.5% of scored vulnerabilities.

Timeline

1. 29-10-2026
   PublishedVulnerability first disclosed.

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.

• CWE-346Origin Validation ErrorThe product does not properly verify that the source of data or communication is valid.
• CWE-942Permissive Cross-domain Security Policy with Untrusted DomainsThe product uses a web-client protection mechanism such as a Content Security Policy (CSP) or cross-domain policy file, but the policy includes untrusted domains with which the web client is allowed to communicate.