CVE-2018-20990: Tar Arbitrary File Overwrite Vulnerability

HIGH
Advisory Identifier: GHSA-2367-c296-3mp2
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CVSS 7.5
CWE-59
Published
Advisory Summary

CVE-2018-20990 is a HIGH (CVSS 7.5) arbitrary file overwrite vulnerability (CWE-59: Improper Link Resolution Before File Access ('Link Following')) affecting Tar libraries in the crates.io ecosystem. The issue involves arbitrary file overwrite in tar-rs. Remediation is available by upgrading affected packages to version 0.4.16.

CVE-2018-20990 at a Glance

CVE Identifier CVE-2018-20990
GHSA Identifier GHSA-2367-c296-3mp2
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-59: Improper Link Resolution Before File Access ('Link Following')
Affected Product Tar
Package Ecosystem crates.io
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:3.0/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-2018-20990

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

tar fixed: 0.4.16 
Upgrade tar to 0.4.16
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 tar

How to Check if You Are Affected

To determine whether your application is affected by CVE-2018-20990, inspect your project dependencies for Tar:

inspect dependencies for tar

Analyze the terminal output to locate any version of Tar in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.4.16), 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-59: Improper Link Resolution Before File Access ('Link Following'), where the product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource. In Tar, 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

When unpacking a tarball with the unpack_in-family of functions it's intended that only files within the specified directory are able to be written. Tarballs with hard links or symlinks, however, can be used to overwrite any file on the filesystem. Tarballs can contain multiple entries for the same file. A tarball which first contains an entry for a hard link or symlink pointing to any file on the filesystem will have the link created, and then afterwards if the same file is listed in the tarball the hard link will be rewritten and any file can be rewritten on the filesystem.

CVE-2018-20990 Affected Tar Versions

1 component(s)
Fixed Versions:
0.4.16
Product / Package Ecosystem Affected Versions Fixed Version
tar
 crates.io
< 0.4.16
0.4.16

References

NVD — CVE-2018-20990 NVD
https://nvd.nist.gov/vuln/detail/CVE-2018-20990
Tar Source Repository REPOSITORY
https://github.com/alexcrichton/tar-rs/pull/156
Security Fix Commit FIX COMMIT
https://github.com/alexcrichton/tar-rs/commit/54651a87ae6ba7d81fcc72ffdee2ea7eca2c7e85
Tar Source Repository REPOSITORY
https://github.com/alexcrichton/tar-rs
rustsec.org/advisories/rustsec-... WEB
https://rustsec.org/advisories/RUSTSEC-2018-0002.html

Frequently Asked Questions

What is CVE-2018-20990?
CVE-2018-20990 is a security vulnerability in Tar involving Arbitrary file overwrite in tar-rs under CWE-59: Improper Link Resolution Before File Access ('Link Following').
Which Tar versions are affected?
Affected versions include releases prior to 0.4.16 across affected packages: tar.
What version fixes CVE-2018-20990?
Upgrading to 0.4.16 (or the latest patched release for your respective branch) resolves the vulnerability.
Is tar affected?
Yes, tar is affected in releases prior to 0.4.16. Upgrade your dependency to 0.4.16 or later.
What is the CVSS score of CVE-2018-20990?
CVE-2018-20990 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.
What CWE is associated with CVE-2018-20990?
CVE-2018-20990 is classified under CWE-59: Improper Link Resolution Before File Access ('Link Following') (The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.).
How can I check crates.io dependencies for CVE-2018-20990?
Run the dependency tree command: 'inspect dependencies for tar'. 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-2367-c296-3mp2",
  "modified" : "2023-06-13T21:53:47Z",
  "published" : "2021-08-25T20:43:54Z",
  "aliases" : [ "CVE-2018-20990" ],
  "summary" : "Arbitrary file overwrite in tar-rs",
  "details" : "When unpacking a tarball with the unpack_in-family of functions it's intended that only files within the specified directory are able to be written. Tarballs with hard links or symlinks, however, can be used to overwrite any file on the filesystem. Tarballs can contain multiple entries for the same file. A tarball which first contains an entry for a hard link or symlink pointing to any file on the filesystem will have the link created, and then afterwards if the same file is listed in the tarball the hard link will be rewritten and any file can be rewritten on the filesystem.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "crates.io",
      "name" : "tar"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.4.16"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2018-20990"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/alexcrichton/tar-rs/pull/156"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/alexcrichton/tar-rs/commit/54651a87ae6ba7d81fcc72ffdee2ea7eca2c7e85"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/alexcrichton/tar-rs"
  }, {
    "type" : "WEB",
    "url" : "https://rustsec.org/advisories/RUSTSEC-2018-0002.html"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-59" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-08-19T21:24:12Z",
    "nvd_published_at" : null
  }
}