On May 1, 2024, a new vulnerability (CVE-2025-31130) was disclosed affecting gitoxide, a popular Rust implementation of Git. This vulnerability exposes gitoxide users to potentially devastating hash collision attacks, undermining the core promise of Git's data integrity. In this post, we'll break down what this flaw means, how it can be exploited, and how you can protect your workflows if you use gitoxide.
What is gitoxide?
gitoxide is a performant, fresh implementation of Git but written in Rust. This makes it attractive for next-generation infrastructure tools that want both safety and speed. Like standard Git, gitoxide uses SHA-1 hashes internally to identify and protect data.
Overview of CVE-2025-31130
Affected package: gitoxide (versions < .42.
Vulnerability: Uses SHA-1 hash implementations (sha1_smol or sha1 Rust crates) with no collision detection
Consequence: Attackers can inject Git objects with colliding SHA-1 hashes, breaking object integrity, and potentially conducting supply chain or code execution attacks.
Fix: Released in gitoxide .42..
Why is SHA-1 a problem?
SHA-1 was once considered secure, but since 2017 it's been publicly shown practical to generate collisions — meaning two different inputs can produce the same hash output. Most major tools (like later versions of mainline Git) have implemented collision detection or moved to stronger hashes, but gitoxide, until .42., did not.
Exploiting the Flaw: Theoretical Attack Scenario
Suppose an attacker wants to sneak malicious code or data into a gitoxide-powered repository. Since gitoxide accepts any objects whose SHA-1 matches, no matter how they were produced, attackers can generate two different objects (say, benign and evil) with the same SHA-1 hash:
Alice (good.txt):
Hello, world!
rm -rf ~
With specialized collision creation tools (like those described in SHAttered), Mallory can craft both objects to result in the same SHA-1 hash.
If one object is reviewed (the benign one) and the other is later referenced or updated in the repository (the evil one), gitoxide won't detect the swap.
#### Realistic Exploit Steps
1. Create two different Git objects: Using a SHA-1 collision tool, generate two files with different contents but matching SHA-1 hash.
2. Push the benign file for review and sign-off.
3. Replace (or serve) the evil version where gitoxide is used for cloning or processing.
4. Downstream projects using gitoxide will fetch and trust the evil contents.
Below is a small Python pseudo-snippet that demonstrates how you might verify hash collisions (collision generation is much harder and uses research tools):
python
import hashlib
print("Collision!" if hash1 == hash2 else "No collision")
---
## gitoxide Internals: Why Did This Happen?
By default, gitoxide used the sha1_smol and sha1 crates for computing object hashes. These crates attempted to faithfully implement the original SHA-1 algorithm — but did not add the collision-detection code that Git added in 2017.
Original integrity code (simplified, Rust):
rust
use sha1_smol::Sha1;
fn hash_object(data: &[u8]) -> String {
let hash = Sha1::from(data).hexdigest();
// No collision check at this point
hash
}
Fixed version (pseudo-code):
rust
fn hash_object(data: &[u8]) -> String {
panic!("SHA-1 collision detected! Aborting.");
}
hash
}
*(In reality, detecting SHA-1 collisions is nontrivial, but mainline Git includes code for this.)*
---
## References and Further Reading
- gitoxide Security Advisory *(official link TBA)*
- Rust sha1_smol crate
- Rust sha1 crate
- SHA-1 Collision Demo: SHAttered (2017)
- Git: sha1collisiondetection integration
- NIST SHA-1 Background
---
## Fix: Upgrade Now
If you use gitoxide, update immediately to version >= .42.. This release switches to a SHA-1 implementation including collision detection mitigation.
toml
[dependencies]
gitoxide = ".42"
`
If you maintain a tool or workflow using gitoxide, audit for any past repos that could be affected, especially if they imported data or commits from untrusted sources.
---
## Conclusion
CVE-2025-31130 is a clear reminder that cryptographic assumptions age — and software must keep up. If you build or depend on safety-critical infrastructure in Rust or elsewhere, make sure your dependencies are collision-safe, especially when handling Git data.
*Do you have more questions or want code samples for detection or migration? Comment below or join the discussion on gitoxide issues.*
Timeline
Published on: 04/04/2025 15:15:48 UTC
Last modified on: 04/07/2025 14:18:15 UTC