A logic error in the ln utility of uutils coreutils causes the program to reject source paths containing non-UTF-8 filename bytes when using target-directory forms (e.g., ln SOURCE… DIRECTORY). While GNU ln treats filenames as raw bytes and creates the links correctly, the uutils implementation enforces UTF-8 encoding, resulting in a failure to stat the file and a non-zero exit code. In environments where automated scripts or system tasks process valid but non-UTF-8 filenames common on Unix filesystems, this divergence causes the utility to fail, leading to a local denial of service for those specific operations.
Weakness
The product does not properly handle when an input contains Unicode encoding.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Coreutils | Uutils | - (including) | - (including) |
| Rust-coreutils | Ubuntu | devel | * |
| Rust-coreutils | Ubuntu | esm-apps/noble | * |
| Rust-coreutils | Ubuntu | noble | * |
| Rust-coreutils | Ubuntu | questing | * |
| Rust-coreutils | Ubuntu | resolute | * |
| Rust-coreutils | Ubuntu | upstream | * |
Potential Mitigations
- Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
- When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
- Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.