Code reviews of the FastFloat crate // Lib.rs

RUSTSEC-2024-0379 (unsound) on 2024-10-31: Multiple soundness issues

fast-float contains multiple soundness issues:

Undefined behavior when checking input length, which has been merged but no package pubished.
Many functions marked as safe with non-local safety guarantees

The library is also unmaintained.

Alternatives

For quickly parsing floating-point numbers third-party crates are generally no longer needed. A fast float parsing algorithm by the author of lexical has been merged into libcore. When requiring direct parsing from bytes and/or partial parsers, the fast-float2 fork of fast-float containing these security patches and reduces overall usage of unsafe.

https://github.com/aldanor/fast-float-rust/issues/28

https://github.com/aldanor/fast-float-rust/issues/37

RUSTSEC-2025-0003 on 2025-01-13: Segmentation fault due to lack of bound check

In this case, the "fast_float::common::AsciiStr::first" method within the "AsciiStr" struct uses the unsafe keyword to reading from memory without performing bounds checking. Specifically, it directly dereferences a pointer offset by "self.ptr". Because of the above reason, the method accesses invalid memory address when it takes an empty string as its input. This approach violates Rust’s memory safety guarantees, as it can lead to invalid memory access if empty buffer is provided.

No patched version for fast-float crate has been released, but a patch is available in the fast-float2 fork.

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0.2.0 (current) ub-risk-4

From google/supply-chain copy of google/rust-crate-audits. By Augie Fackler, manishearth.

Reviewed in Issues found:

https://github.com/aldanor/fast-float-rust/issues/37 (multiple issues)

0.2.0 (current) unknown

From kornelski/crev-proofs copy of git.savannah.gnu.org.

Packaged for Guix (crates-io)

cargo-vet does not verify reviewers' identity. You have to fully trust the source the audits are from.

ub-risk-4

Extreme unsoundness.

Full description of the audit criteria can be found at https://github.com/google/rust-crate-audits/blob/main/auditing_standards.md#ub-risk-4

unknown

May have been packaged automatically without a review

Lib.rs has been able to verify that all files in the crate's tarball are in the crate's repository with a git tag matching the version. Please note that this check is still in beta, and absence of this confirmation does not mean that the files don't match.

Crates in the crates.io registry are tarball snapshots uploaded by crates' publishers. The registry is not using crates' git repositories, so there is a possibility that published crates have a misleading repository URL, or contain different code from the code in the repository.

To review the actual code of the crate, it's best to use cargo crev open fast-float. Alternatively, you can download the tarball of fast-float v0.2.0 or view the source online.