CVE-2021-39208: SharpCompress is a fully managed C# library to deal with many compression types and formats. Versions prior to 0.29.0 are vulnerable to partial path t...

Description

SharpCompress is a fully managed C# library to deal with many compression types and formats. Versions prior to 0.29.0 are vulnerable to partial path traversal. SharpCompress recreates a hierarchy of directories under destinationDirectory if ExtractFullPath is set to true in options. In order to prevent extraction outside the destination directory the destinationFileName path is verified to begin with fullDestinationDirectoryPath. However, prior to version 0.29.0, it is not enforced that fullDestinationDirectoryPath ends with slash. If the destinationDirectory is not slash terminated like `/home/user/dir` it is possible to create a file with a name thats begins as the destination directory one level up from the 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. This issue is fixed in SharpCompress version 0.29.0.

Metrics

CVSS 3.1

4.3/10

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

EPSS Probability

1.15%

63.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-22

Affected Software

Vendor	Product	Versions
Sharpcompress Project	Sharpcompress	< 0.29.0

References

https://github.com/adamhathcock/sharpcompress/pull/614Patch, Third Party Advisory
https://github.com/adamhathcock/sharpcompress/releases/tag/0.29.0Release Notes, Third Party Advisory
https://github.com/adamhathcock/sharpcompress/security/advisories/GHSA-jp7f-grcv-6mjfExploit, Third Party Advisory
https://github.com/adamhathcock/sharpcompress/pull/614Patch, Third Party Advisory
https://github.com/adamhathcock/sharpcompress/releases/tag/0.29.0Release Notes, Third Party Advisory
https://github.com/adamhathcock/sharpcompress/security/advisories/GHSA-jp7f-grcv-6mjfExploit, Third Party Advisory

Timeline

Published: Sep 16, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-39208?

SharpCompress is a fully managed C# library to deal with many compression types and formats. Versions prior to 0.29.0 are vulnerable to partial path traversal. SharpCompress recreates a hierarchy of directories under destinationDirectory if ExtractFullPath is set to true in options. In order to prevent extraction outside the destination directory the destinationFileName path is verified to begin with fullDestinationDirectoryPath. However, prior to version 0.29.0, it is not enforced that fullDestinationDirectoryPath ends with slash. If the destinationDirectory is not slash terminated like `/home/user/dir` it is possible to create a file with a name thats begins as the destination directory one level up from the 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. This issue is fixed in SharpCompress version 0.29.0.

How severe is CVE-2021-39208?

CVE-2021-39208 has a CVSS score of 4.3/10 (MEDIUM severity). The EPSS model estimates a 1.15% probability of exploitation in the next 30 days.

How do I fix CVE-2021-39208?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.