Package Instance

go-git missing validation decoding Index v4 files leads to panic
### Impact

`go-git`’s index decoder for format version 4 fails to validate the path name prefix length before applying it to the previously decoded path name. A maliciously crafted index file can trigger an out-of-bounds slice operation, resulting in a runtime panic during normal index parsing.

This issue only affects Git index format version 4. Earlier formats (`go-git` supports only `v2` and `v3`) are not vulnerable to this issue.

An attacker able to supply a crafted `.git/index` file can cause applications using go-git to panic while reading the index. If the application does not recover from panics, this results in process termination, leading to a denial-of-service (DoS) condition.

Exploitation requires the ability to modify or inject a Git index file within the local repository in disk. This typically implies write access to the `.git` directory.

### Patches

Users should upgrade to `v5.17.1`, or the latest `v6` [pseudo-version](https://go.dev/ref/mod#pseudo-versions), in order to mitigate this vulnerability.

### Credit

go-git maintainers thank @kq5y for finding and reporting this issue privately to the `go-git` project.

go-git improperly verifies data integrity values for .idx and .pack files
### Impact 

A vulnerability was discovered in `go-git` whereby data integrity values for `.pack` and `.idx` files were not properly verified. This resulted in `go-git` potentially consuming corrupted files, which would likely result in unexpected errors such as `object not found`.

For context, clients fetch [`packfiles`](https://git-scm.com/docs/pack-protocol#_packfile_data) from upstream Git servers. Those files contain a checksum of their contents, so that clients can perform integrity checks before consuming it. The pack indexes (`.idx`) are [generated](https://git-scm.com/docs/pack-format) locally by `go-git`, or the `git` cli, when new `.pack` files are received and processed. The integrity checks for both files were not being verified correctly.

Note that the lack of verification of the packfile checksum has no impact on the trust relationship between the client and server, which is enforced based on the protocol being used (e.g. TLS in the case of `https://` or known hosts for `ssh://`). In other words, the packfile checksum verification does not provide any security benefits when connecting to a malicious or compromised Git server.

### Patches

Users should upgrade to `v5.16.5`, or the latest `v6` [pseudo-version](https://go.dev/ref/mod#pseudo-versions), in order to mitigate this vulnerability.

### Workarounds

In case updating to a fixed version of `go-git` is not possible, users can run [git fsck](https://git-scm.com/docs/git-fsck) from the `git` cli to check for data corruption on a given repository. 

### Credit

Thanks @N0zoM1z0 for finding and reporting this issue privately to the `go-git` project.

go-git: Maliciously crafted idx file can cause asymmetric memory consumption
### Impact

A vulnerability has been identified in which a maliciously crafted `.idx` file can cause asymmetric memory consumption, potentially exhausting available memory and resulting in a Denial of Service (DoS) condition.

Exploitation requires write access to the local repository's `.git` directory, it order to create or alter existing `.idx` files. 

### Patches

Users should upgrade to `v5.17.1`, or the latest `v6` [pseudo-version](https://go.dev/ref/mod#pseudo-versions), in order to mitigate this vulnerability.

### Credit

The go-git maintainers thank @kq5y for finding and reporting this issue privately to the `go-git` project.