CVE-2021-28966: Tmpdir Path Traversal Vulnerability

HIGH
Advisory Identifier: GHSA-46f2-3v63-3xrp
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CVSS 7.5
CWE-22
Published
Advisory Summary

CVE-2021-28966 is a HIGH (CVSS 7.5) path traversal vulnerability (CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')) affecting Tmpdir libraries in the RubyGems ecosystem. The issue involves tempfile on windows path traversal vulnerability. Remediation is available by upgrading affected packages to version 0.1.2.

CVE-2021-28966 at a Glance

CVE Identifier CVE-2021-28966
GHSA Identifier GHSA-46f2-3v63-3xrp
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Affected Product Tmpdir
Package Ecosystem RubyGems
Published Date
Last Updated

Security Impact

CVSS: 7.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N).

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 None (C:N)
Integrity High (I:H)
Availability None (A:N)

How to Fix CVE-2021-28966

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

tmpdir fixed: 0.1.2 
Upgrade tmpdir to 0.1.2
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 tmpdir

How to Check if You Are Affected

To determine whether your application is affected by CVE-2021-28966, inspect your project dependencies for Tmpdir:

inspect dependencies for tmpdir

Analyze the terminal output to locate any version of Tmpdir in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.1.2), 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-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal'), where the product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. In Tmpdir, 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

There is an unintentional directory creation vulnerability in `tmpdir` library bundled with Ruby on Windows. And there is also an unintentional file creation vulnerability in tempfile library bundled with Ruby on Windows, because it uses tmpdir internally.

CVE-2021-28966 Affected Tmpdir Versions

1 component(s)
Fixed Versions:
0.1.2
Product / Package Ecosystem Affected Versions Fixed Version
tmpdir
gem/tmpdir
RubyGems
< 0.1.2
0.1.2

References

NVD — CVE-2021-28966 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-28966
Tmpdir Source Repository REPOSITORY
https://github.com/ruby/tmpdir/pull/8
Security Fix Commit FIX COMMIT
https://github.com/ruby/tmpdir/commit/93798c01cb7c10476e50a4d80130a329ba47f348
hackerone.com/reports/1131465 WEB
https://hackerone.com/reports/1131465
Tmpdir Source Repository REPOSITORY
https://github.com/ruby/tmpdir
Tmpdir Source Repository REPOSITORY
https://github.com/rubysec/ruby-advisory-db/blob/master/gems/tmpdir/CVE-2021-28966.yml
rubygems.org/gems/tmpdir WEB
https://rubygems.org/gems/tmpdir
Tmpdir Security Information SECURITY
https://security.netapp.com/advisory/ntap-20210902-0004
www.ruby-lang.org/en/news/2021/04/05/... WEB
https://www.ruby-lang.org/en/news/2021/04/05/tempfile-path-traversal-on-windows-cve-2021-28966

Frequently Asked Questions

What is CVE-2021-28966?
CVE-2021-28966 is a security vulnerability in Tmpdir involving Tempfile on Windows path traversal vulnerability under CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal').
Which Tmpdir versions are affected?
Affected versions include releases prior to 0.1.2 across affected packages: tmpdir.
What version fixes CVE-2021-28966?
Upgrading to 0.1.2 (or the latest patched release for your respective branch) resolves the vulnerability.
Is tmpdir affected?
Yes, tmpdir is affected in releases prior to 0.1.2. Upgrade your dependency to 0.1.2 or later.
What is the CVSS score of CVE-2021-28966?
CVE-2021-28966 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.
What CWE is associated with CVE-2021-28966?
CVE-2021-28966 is classified under CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') (The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.).
How can I check RubyGems dependencies for CVE-2021-28966?
Run the dependency tree command: 'inspect dependencies for tmpdir'. 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-46f2-3v63-3xrp",
  "modified" : "2022-08-15T20:01:42Z",
  "published" : "2021-05-06T15:01:36Z",
  "aliases" : [ "CVE-2021-28966" ],
  "summary" : "Tempfile on Windows path traversal vulnerability",
  "details" : "There is an unintentional directory creation vulnerability in `tmpdir` library bundled with Ruby on Windows. And there is also an unintentional file creation vulnerability in tempfile library bundled with Ruby on Windows, because it uses tmpdir internally. \n",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "RubyGems",
      "name" : "tmpdir"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.1.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-28966"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/ruby/tmpdir/pull/8"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/ruby/tmpdir/commit/93798c01cb7c10476e50a4d80130a329ba47f348"
  }, {
    "type" : "WEB",
    "url" : "https://hackerone.com/reports/1131465"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/ruby/tmpdir"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rubysec/ruby-advisory-db/blob/master/gems/tmpdir/CVE-2021-28966.yml"
  }, {
    "type" : "WEB",
    "url" : "https://rubygems.org/gems/tmpdir"
  }, {
    "type" : "WEB",
    "url" : "https://security.netapp.com/advisory/ntap-20210902-0004"
  }, {
    "type" : "WEB",
    "url" : "https://www.ruby-lang.org/en/news/2021/04/05/tempfile-path-traversal-on-windows-cve-2021-28966"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-22" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-05-06T15:01:12Z",
    "nvd_published_at" : "2021-07-30T14:15:00Z"
  }
}