CVE-2020-27534: Github.com/moby/moby Path Traversal Vulnerability

MODERATE
Advisory Identifier: GHSA-6hwg-w5jg-9c6x
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CVSS 5.3
CWE-22
Published
Advisory Summary

CVE-2020-27534 is a MODERATE (CVSS 5.3) path traversal vulnerability (CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')) affecting Github.com/moby/moby libraries in the Go ecosystem. The issue involves path traversal in moby builder. Remediation is available by upgrading affected packages to version 19.03.9.

CVE-2020-27534 at a Glance

CVE Identifier CVE-2020-27534
GHSA Identifier GHSA-6hwg-w5jg-9c6x
Severity MODERATE
CVSS v3.1 Base Score 5.3
CWE Classification CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Affected Product Github.com/moby/moby
Package Ecosystem Go
Published Date
Last Updated

Security Impact

CVSS: 5.3

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:L/I:N/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 Low (C:L)
Integrity None (I:N)
Availability None (A:N)

How to Fix CVE-2020-27534

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

github.com/moby/moby fixed: 19.03.9 
Upgrade github.com/moby/moby to 19.03.9
github.com/docker/docker fixed: 19.03.9 
Upgrade github.com/docker/docker to 19.03.9
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 github.com/moby/moby

How to Check if You Are Affected

To determine whether your application is affected by CVE-2020-27534, inspect your project dependencies for Github.com/moby/moby:

inspect dependencies for github.com/moby/moby

Analyze the terminal output to locate any version of Github.com/moby/moby in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 19.03.9), 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 Github.com/moby/moby, 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

util/binfmt_misc/check.go in Builder in Docker Engine before 19.03.9 calls os.OpenFile with a potentially unsafe qemu-check temporary pathname, constructed with an empty first argument in an ioutil.TempDir call.

CVE-2020-27534 Affected Github.com/moby/moby Versions

2 component(s)
Fixed Versions:
19.03.9
Product / Package Ecosystem Affected Versions Fixed Version
github.com/moby/moby
golang/github.com/moby/moby
Go
< 19.03.9
19.03.9
github.com/docker/docker
golang/github.com/docker/docker
Go
< 19.03.9
19.03.9

References

NVD — CVE-2020-27534 NVD
https://nvd.nist.gov/vuln/detail/CVE-2020-27534
Github.com/moby/moby Source Repository REPOSITORY
https://github.com/moby/buildkit/pull/1462
Github.com/moby/moby Source Repository REPOSITORY
https://github.com/moby/moby/pull/40877
bugzilla.redhat.com/show_bug.cgi WEB
https://bugzilla.redhat.com/show_bug.cgi?id=1921154
web.archive.org/web/20200530054359/... WEB
http://web.archive.org/web/20200530054359/https://docs.docker.com/engine/release-notes

Frequently Asked Questions

What is CVE-2020-27534?
CVE-2020-27534 is a security vulnerability in Github.com/moby/moby involving Path Traversal in Moby builder under CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal').
Which Github.com/moby/moby versions are affected?
Affected versions include releases prior to 19.03.9 across affected packages: github.com/moby/moby, github.com/docker/docker.
What version fixes CVE-2020-27534?
Upgrading to 19.03.9 (or the latest patched release for your respective branch) resolves the vulnerability.
Is github.com/moby/moby affected?
Yes, github.com/moby/moby is affected in releases prior to 19.03.9. Upgrade your dependency to 19.03.9 or later.
Is github.com/docker/docker affected?
Yes, github.com/docker/docker is affected in releases prior to 19.03.9. Upgrade your dependency to 19.03.9 or later.
What is the CVSS score of CVE-2020-27534?
CVE-2020-27534 has a CVSS v3.1 base score of 5.3 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N.
What CWE is associated with CVE-2020-27534?
CVE-2020-27534 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 Go dependencies for CVE-2020-27534?
Run the dependency tree command: 'inspect dependencies for github.com/moby/moby'. 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-6hwg-w5jg-9c6x",
  "modified" : "2024-04-22T19:08:25Z",
  "published" : "2024-01-31T23:13:10Z",
  "aliases" : [ "CVE-2020-27534" ],
  "summary" : "Path Traversal in Moby builder",
  "details" : "util/binfmt_misc/check.go in Builder in Docker Engine before 19.03.9 calls os.OpenFile with a potentially unsafe qemu-check temporary pathname, constructed with an empty first argument in an ioutil.TempDir call.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/moby/moby"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "19.03.9"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/docker/docker"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "19.03.9"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2020-27534"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/moby/buildkit/pull/1462"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/moby/moby/pull/40877"
  }, {
    "type" : "WEB",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=1921154"
  }, {
    "type" : "WEB",
    "url" : "http://web.archive.org/web/20200530054359/https://docs.docker.com/engine/release-notes"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-22" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2024-01-31T23:13:10Z",
    "nvd_published_at" : null
  }
}