UBUNTU-CVE-2026-35374: Medium severity ubuntu/rust-coreutils vulnerability
A Time-of-Check to Time-of-Use (TOCTOU) vulnerability exists in the split utility of uutils coreutils. The program attempts to prevent data loss by checking for identity between input and output files using their file paths before initiating the split operation. However, the utility subsequently opens the output file with truncation after this path-based validation is complete. A local attacker with write access to the directory can exploit this race window by manipulating mutable path components (e.g., swapping a path with a symbolic link). This can cause split to truncate and write to an unintended target file, potentially including the input file itself or other sensitive files accessible to the process, leading to permanent data loss.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
ubuntu/rust-coreutilsto a version that resolves this vulnerability.Fixed in 0.10.0-1ubuntu1
Event History
Frequently Asked Questions
Who is realistically exposed to this issue?
Systems are exposed when they run the split utility from Ubuntu's rust-coreutils package on files in directories writable by a local attacker. The attacker must be able to manipulate mutable path components involved in the input or output path.
What does an attacker need to exploit it?
Exploitation requires local access, low privileges, and write access to the relevant directory. The attacker must win a race after split validates the input and output paths but before it opens the output file for truncation.
What is the likely impact if exploitation succeeds?
The attacker can redirect output handling to an unintended file that the split process can access. This can permanently truncate or overwrite the input file or another sensitive accessible file, affecting integrity and availability.
What can be done if patching is not immediately possible?
Avoid running split with input or output paths whose directories are writable by untrusted local users. Use directories with controlled ownership and permissions, and avoid mutable path components such as attacker-controlled symbolic links.