EUVD-2026-270489

fkie_cve-2026-25882

Fiber is an Express inspired web framework written in Go. A denial of service vulnerability exists in Fiber v2 and v3 that allows remote attackers to crash the application by sending requests to routes with more than 30 parameters. The vulnerability results from missing validation during route registration combined with an unbounded array write during request matching. Version 2.52.12 patches the issue in the v2 branch and 3.1.0 patches the issue in the v3 branch.

GHSA-mrq8-rjmw-wpq3 — Fiber has a Denial of Service Vulnerability via Route Parameter Overflow

Affected: Go: github.com/gofiber/fiber/v2, Go: github.com/gofiber/fiber/v3

A denial of service vulnerability exists in Fiber v2 and v3 that allows remote attackers to crash the application by sending requests to routes with more than 30 parameters. The vulnerability results from missing validation during route registration combined with an unbounded array write during request matching.

## Affected Versions

- **Fiber v3.0.0-rc.3** and earlier v3 releases - **Fiber v2.52.10** and potentially all v2 releases (confirmed exploitable) - Both versions share the same vulnerable routing implementation

## Vulnerability Details

### Root Cause

Both Fiber v2 and v3 define a fixed-size parameter array in `ctx.go`:

```go const maxParams = 30

type DefaultCtx struct { values [maxParams]string // Fixed 30-element array // ... } ```

The `router.go` `register()` function accepts routes without validating parameter count. When a request matches a route exceeding 30 parameters, the code in `path.go` performs an unbounded write:

- **v3**: `path.go:514` - **v2**: `path.go:516`

```go // path.go:514 - NO BOUNDS CHECKING params[paramsIterator] = path[:i] ```

When `paramsIterator >= 30`, this triggers: ``` panic: runtime error: index out of range [30] with length 30 ```

### Attack Scenario

1. Application registers route with >30 parameters (e.g., via code or dynamic routing): ```go app.Get("/api/:p1/:p2/:p3/.../p35", handler) ```

2. Attacker sends matching HTTP request: ```bash curl http://target/api/v1/v2/v3/.../v35 ```

3. Server cra…

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EUVD-2026-270489

fkie_cve-2026-25882

GHSA-mrq8-rjmw-wpq3 — Fiber has a Denial of Service Vulnerability via Route Parameter Overflow