CVE-2017-9785: Nancy Deserialization Of Untrusted Data Vulnerability

CRITICAL
Advisory Identifier: GHSA-mx3q-j2g2-5qxq
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CVSS 9.8
CWE-502
Published
Advisory Summary

CVE-2017-9785 is a CRITICAL (CVSS 9.8) deserialization of untrusted data vulnerability (CWE-502: Deserialization of Untrusted Data) affecting Nancy libraries in the NuGet ecosystem. The issue involves deserialization of untrusted data in nancyfx nancy. Remediation is available by upgrading affected packages to version 1.4.4, 2.0.0.

CVE-2017-9785 at a Glance

CVE Identifier CVE-2017-9785
GHSA Identifier GHSA-mx3q-j2g2-5qxq
Severity CRITICAL
CVSS v3.1 Base Score 9.8
CWE Classification CWE-502: Deserialization of Untrusted Data
Affected Product Nancy
Package Ecosystem NuGet
Published Date
Last Updated

Security Impact

CVSS: 9.8

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity High (I:H)
Availability High (A:H)

How to Fix CVE-2017-9785

To remediate this vulnerability, upgrade all affected Nancy dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

Nancy fixed: 1.4.4 
Upgrade Nancy to 1.4.4
Nancy fixed: 2.0.0 
Upgrade Nancy to 2.0.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for Nancy

How to Check if You Are Affected

To determine whether your application is affected by CVE-2017-9785, inspect your project dependencies for Nancy:

inspect dependencies for Nancy

Analyze the terminal output to locate any version of Nancy in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.4.4), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-502: Deserialization of Untrusted Data, where the product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid. In Nancy, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

Csrf.cs in NancyFX Nancy before 1.4.4 and 2.x before 2.0-dangermouse has Remote Code Execution via Deserialization of JSON data in a CSRF Cookie.

CVE-2017-9785 Affected Nancy Versions

2 component(s)
Fixed Versions:
1.4.42.0.0
Product / Package Ecosystem Affected Versions Fixed Version
Nancy
nuget/Nancy
NuGet
< 1.4.4
1.4.4
Nancy
nuget/Nancy
NuGet
≥ 2.0.0-alpha
< 2.0.0
2.0.0

References

NVD — CVE-2017-9785 NVD
https://nvd.nist.gov/vuln/detail/CVE-2017-9785
Nancy Release RELEASE
https://github.com/NancyFx/Nancy/releases/tag/v1.4.4

Frequently Asked Questions

What is CVE-2017-9785?
CVE-2017-9785 is a security vulnerability in Nancy involving Deserialization of Untrusted Data in NancyFX Nancy under CWE-502: Deserialization of Untrusted Data.
Which Nancy versions are affected?
Affected versions include releases prior to 1.4.4, 2.0.0 across affected packages: Nancy.
What version fixes CVE-2017-9785?
Upgrading to 1.4.4, 2.0.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is Nancy affected?
Yes, Nancy is affected in releases prior to 1.4.4, 2.0.0. Upgrade your dependency to 1.4.4, 2.0.0 or later.
What is the CVSS score of CVE-2017-9785?
CVE-2017-9785 has a CVSS v3.1 base score of 9.8 (CRITICAL) with vector string CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2017-9785?
CVE-2017-9785 is classified under CWE-502: Deserialization of Untrusted Data (The product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid.).
How can I check NuGet dependencies for CVE-2017-9785?
Run the dependency tree command: 'inspect dependencies for Nancy'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-mx3q-j2g2-5qxq",
  "modified" : "2022-06-30T19:51:21Z",
  "published" : "2022-05-17T02:26:07Z",
  "aliases" : [ "CVE-2017-9785" ],
  "summary" : "Deserialization of Untrusted Data in NancyFX Nancy",
  "details" : "Csrf.cs in NancyFX Nancy before 1.4.4 and 2.x before 2.0-dangermouse has Remote Code Execution via Deserialization of JSON data in a CSRF Cookie.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "NuGet",
      "name" : "Nancy"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.4.4"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 1.4.3"
    }
  }, {
    "package" : {
      "ecosystem" : "NuGet",
      "name" : "Nancy"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.0.0-alpha"
      }, {
        "fixed" : "2.0.0"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 2.0.0-clinteastwood"
    }
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2017-9785"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/NancyFx/Nancy/releases/tag/v1.4.4"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-502" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2022-06-30T19:51:21Z",
    "nvd_published_at" : "2017-07-20T12:29:00Z"
  }
}