# CVE-2026-119285: Fiber CORS middleware wildcard domain bypass

Source: https://junglewise.ai/threats/cve-2026-119285-fiber-is-an-express-inspired-web-framework-written-in-go-from-2  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-29. Updated: 2026-10-29  
License: CC BY 4.0 with a link back

CVE-2026-119285 · Severity: medium · CVSS 5.9 · Published 2026-10-29

Fiber is a Go web framework with a CORS middleware that validates which origins can access cross-origin resources. The middleware's wildcard subdomain matching was flawed, allowing an attacker to craft a malicious origin that ends with a legitimate domain to bypass restrictions. When a user visits the attacker's page, authenticated responses from the legitimate origin can be exposed to the attacker.

Technologies: [github.com/gofiber/fiber/v2 (Go)](https://junglewise.ai/threats/technologies/github-com-gofiber-fiber-v2). Vendors: [Go](https://junglewise.ai/threats/vendors/go), [Gofiber](https://junglewise.ai/threats/vendors/gofiber).

## Quick answers

**Is CVE-2026-119285 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-119285 being exploited in the wild.

**How severe is CVE-2026-119285?** Medium severity, with a CVSS score of 5.9, published 29 October 2026.

**Which products and versions are affected?** github.com/gofiber/fiber/v2 (Go) >= 2.52.1, <= 2.52.2, SEMVER:introduced=2.52.1,fixed=2.52.3; Gofiber Fiber 2.52.1 through 2.52.2.

**Is there a fix for CVE-2026-119285?** Yes. github.com/gofiber/fiber/v2 (Go): upgrade to 2.52.3 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-119285 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-119285?** Check whether you run github.com/gofiber/fiber/v2 (Go) or Gofiber Fiber at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- github.com/gofiber/fiber/v2 (Go): upgrade to 2.52.3 or later

  ```sh
  go get github.com/gofiber/fiber/v2@v2.52.3
  ```


## Technical details

The validateDomain function in middleware/cors/utils.go improperly matches wildcard subdomain patterns by stripping the scheme and checking only a host suffix without requiring a dot boundary. This allows an attacker to register or control a domain like "legitimate-domain.com" to match a policy intended for "*.legitimate-domain.com". The vulnerability requires AllowCredentials to be enabled and a wildcard-subdomain AllowOrigins configuration; the attacker exploits it via reflected origin headers, exposing authenticated cross-origin responses.

## Affected products

- gofiber Fiber 2.52.1 through 2.52.2

## Identifiers

- CVE-2026-119285
- GHSA-g5jq-qmqr-qrwf
- GO-2026-6896

## Timeline

- 2026-10-29: disclosed

## References

- [https://github.com/gofiber/fiber/commit/1aac6f618b6bd3e159d2449acb4232a2170b976b](https://github.com/gofiber/fiber/commit/1aac6f618b6bd3e159d2449acb4232a2170b976b)
- [https://github.com/gofiber/fiber/pull/2915](https://github.com/gofiber/fiber/pull/2915)

## Related threats

- [Gofiber Fiber IP spoofing in BalancerForward proxy helper](https://junglewise.ai/threats/cve-2026-45045-gofiber-fiber-ip-spoofing-in-balancerforward-proxy-helper)
- [Go Fiber XSS in AutoFormat content negotiation](https://junglewise.ai/threats/cve-2026-42554-go-fiber-xss-in-autoformat-content-negotiation)
- [GO-2026-4543 - Fiber has a Denial of Service Vulnerability via Route Parameter Overflow in github.com/gofiber/fiber](https://junglewise.ai/threats/cve-2026-25882-fiber-has-a-denial-of-service-vulnerability-via-route-parameter)
- [GO-2026-4471 - Fiber has an insecure fallback in utils.UUIDv4() / utils.UUID() on crypto/rand failure in github.com/gofiber/fiber](https://junglewise.ai/threats/cve-2025-66630-fiber-has-an-insecure-fallback-in-utils-uuidv4-utils-uuid)
- [GO-2025-3845 - Fiber Crashes in BodyParser Due to Unvalidated Large Slice Index in Decoder in github.com/gofiber/fiber](https://junglewise.ai/threats/cve-2025-54801-fiber-crashes-in-bodyparser-due-to-unvalidated-large-slice-index)