CVE-2021-39208 WriteEntryToDirectory used for an archive extraction is vulnerable to partial path traversal.
Attackers can create files outside the intended directory if ExtractFullPath is enabled and the destination path lacks a trailing slash.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2021-39208?
CVE-2021-39208 is a medium-severity path traversal vulnerability in adamhathcock sharpcompress, published on 16 Sep 2021. Any signed-in user can exploit it over the network, with no action from the victim.
Official 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.
Weakness: CWE-22
Which versions are affected by CVE-2021-39208?
2 open source packages ship an affected version, including SharpCompress. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
SharpCompress NuGet | All versions | 0.29 |
SharpCompress NuGet | All versions | 0.29 |
Products include Sharpcompress Project Sharpcompress.
How do I fix CVE-2021-39208?
Upgrade SharpCompress to 0.29 or later.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2021-39208 being exploited?
There is no known exploitation of CVE-2021-39208 in the wild and no public exploit code.
Sources
Also known as ECHO-f206-fe3f-2dda, GHSA-jp7f-grcv-6mjf.