CVE-2021-32841: SharpZipLib Path Traversal Vulnerability

MODERATE
Advisory Identifier: GHSA-2x7h-96h5-rq84
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CVSS 4.0
CWE-22
Published
Advisory Summary

CVE-2021-32841 is a MODERATE (CVSS 4.0) path traversal vulnerability (CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')) affecting SharpZipLib libraries in the NuGet ecosystem. The issue involves path traversal in sharpziplib. Remediation is available by upgrading affected packages to version 1.3.3.

CVE-2021-32841 at a Glance

CVE Identifier CVE-2021-32841
GHSA Identifier GHSA-2x7h-96h5-rq84
Severity MODERATE
CVSS v3.1 Base Score 4.0
CWE Classification CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Affected Product SharpZipLib
Package Ecosystem NuGet
Published Date
Last Updated

Security Impact

CVSS: 4.0

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

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

How to Fix CVE-2021-32841

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

SharpZipLib fixed: 1.3.3 
Upgrade SharpZipLib to 1.3.3
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 SharpZipLib

How to Check if You Are Affected

To determine whether your application is affected by CVE-2021-32841, inspect your project dependencies for SharpZipLib:

inspect dependencies for SharpZipLib

Analyze the terminal output to locate any version of SharpZipLib in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.3.3), 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 SharpZipLib, 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

SharpZipLib (or #ziplib) is a Zip, GZip, Tar and BZip2 library. Starting version 1.3.0 and prior to version 1.3.3, a check was added if the destination file is under destination directory. However, it is not enforced that `destDir` ends with slash. If the `destDir` is not slash terminated like `/home/user/dir` it is possible to create a file with a name thats begins with the destination directory, i.e. `/home/user/dir.sh`. Because of the file name and destination directory constraints, the arbitrary file creation impact is limited and depends on the use case. Version 1.3.3 contains a patch for this vulnerability.

CVE-2021-32841 Affected SharpZipLib Versions

1 component(s)
Fixed Versions:
1.3.3
Product / Package Ecosystem Affected Versions Fixed Version
SharpZipLib
nuget/SharpZipLib
NuGet
≥ 1.3.0
< 1.3.3
1.3.3

References

NVD — CVE-2021-32841 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-32841
Security Fix Commit FIX COMMIT
https://github.com/icsharpcode/SharpZipLib/commit/5c3b293de5d65b108e7f2cd0ea8f81c1b8273f78
SharpZipLib Source Repository REPOSITORY
https://github.com/icsharpcode/SharpZipLib
SharpZipLib Release RELEASE
https://github.com/icsharpcode/SharpZipLib/releases/tag/v1.3.3
GitHub Advisory / Wiki ADVISORY
https://securitylab.github.com/advisories/GHSL-2021-125-sharpziplib

Frequently Asked Questions

What is CVE-2021-32841?
CVE-2021-32841 is a security vulnerability in SharpZipLib involving Path Traversal in SharpZipLib under CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal').
Which SharpZipLib versions are affected?
Affected versions include releases prior to 1.3.3 across affected packages: SharpZipLib.
What version fixes CVE-2021-32841?
Upgrading to 1.3.3 (or the latest patched release for your respective branch) resolves the vulnerability.
Is SharpZipLib affected?
Yes, SharpZipLib is affected in releases prior to 1.3.3. Upgrade your dependency to 1.3.3 or later.
What is the CVSS score of CVE-2021-32841?
CVE-2021-32841 has a CVSS v3.1 base score of 4.0 (MODERATE) with vector string CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N.
What CWE is associated with CVE-2021-32841?
CVE-2021-32841 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 NuGet dependencies for CVE-2021-32841?
Run the dependency tree command: 'inspect dependencies for SharpZipLib'. 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-2x7h-96h5-rq84",
  "modified" : "2022-02-08T19:44:44Z",
  "published" : "2022-02-01T16:22:57Z",
  "aliases" : [ "CVE-2021-32841" ],
  "summary" : "Path Traversal in SharpZipLib",
  "details" : "SharpZipLib (or #ziplib) is a Zip, GZip, Tar and BZip2 library. Starting version 1.3.0 and prior to version 1.3.3, a check was added if the destination file is under destination directory. However, it is not enforced that `destDir` ends with slash. If the `destDir` is not slash terminated like `/home/user/dir` it is possible to create a file with a name thats begins with the destination directory, i.e. `/home/user/dir.sh`. Because of the file name and destination directory constraints, the arbitrary file creation impact is limited and depends on the use case. Version 1.3.3 contains a patch for this vulnerability.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "NuGet",
      "name" : "SharpZipLib"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.3.0"
      }, {
        "fixed" : "1.3.3"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-32841"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/icsharpcode/SharpZipLib/commit/5c3b293de5d65b108e7f2cd0ea8f81c1b8273f78"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/icsharpcode/SharpZipLib"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/icsharpcode/SharpZipLib/releases/tag/v1.3.3"
  }, {
    "type" : "ADVISORY",
    "url" : "https://securitylab.github.com/advisories/GHSL-2021-125-sharpziplib"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-22" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2022-02-01T16:21:00Z",
    "nvd_published_at" : "2022-01-26T22:15:00Z"
  }
}