GHSA-3669-72x9-r9p3

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Source
https://github.com/advisories/GHSA-3669-72x9-r9p3
Import Source
https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2024/07/GHSA-3669-72x9-r9p3/GHSA-3669-72x9-r9p3.json
JSON Data
https://api.osv.dev/v1/vulns/GHSA-3669-72x9-r9p3
Aliases
Published
2024-07-01T20:35:12Z
Modified
2024-07-05T21:29:07Z
Severity
  • 7.5 (High) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H CVSS Calculator
Summary
Potential memory exhaustion attack due to sparse slice deserialization
Details

Details

Running schema.Decoder.Decode() on a struct that has a field of type []struct{...} opens it up to malicious attacks regarding memory allocations, taking advantage of the sparse slice functionality. For instance, in the Proof of Concept written below, someone can specify to set a field of the billionth element and it will allocate all other elements before it in the slice.

In the local environment environment for my project, I was able to call an endpoint like /innocent_endpoint?arr.10000000.X=1 and freeze my system from the memory allocation while parsing r.Form. I think this line is responsible for allocating the slice, although I haven't tested to make sure, so it's just an educated guess.

Proof of Concept

The following proof of concept works on both v1.2.0 and v1.2.1. I have not tested earlier versions.

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)
}

Impact

Any use of schema.Decoder.Decode() on a struct with arrays of other structs could be vulnerable to this memory exhaustion vulnerability. There seems to be no possible solution that a developer using this library can do to disable this behaviour without fixing it in this project, so all uses of Decode that fall under this umbrella are affected. A fix that doesn't require a major change may also be harder to find, since it could break compatibility with some other intended use-cases.

References

Affected packages

Go / github.com/gorilla/schema

Package

Name
github.com/gorilla/schema
View open source insights on deps.dev
Purl
pkg:golang/github.com/gorilla/schema

Affected ranges

Type
SEMVER
Events
Introduced
0Unknown introduced version / All previous versions are affected
Fixed
1.4.1