UBUNTU-CVE-2026-35357: Race Condition
The cp utility in uutils coreutils is vulnerable to an information disclosure race condition. Destination files are initially created with umask-derived permissions (e.g., 0644) before being restricted to their final mode (e.g., 0600) later in the process. A local attacker can race to open the file during this window; once obtained, the file descriptor remains valid and readable even after the permissions are tightened, exposing sensitive or private file contents.
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 0.10.0-1ubuntu2~26.04.1
Event History
Frequently Asked Questions
Who is exposed to this issue?
Systems using the cp utility from Ubuntu's rust-coreutils package are exposed when sensitive content is copied to a destination that is initially created with permissions allowing a local attacker to open it. The attacker must have local access to race the file creation and permission-change window.
What does an attacker need to do to exploit it?
The attacker needs local access, low privileges sufficient to monitor and open the destination file, and successful timing during the brief interval before cp restricts the file to its final permissions. No user interaction is required.
Does tightening the destination file permissions after copying prevent disclosure?
No. If an attacker opens the destination while it has the initial umask-derived permissions, the obtained file descriptor remains readable after cp changes the file mode, allowing the copied contents to be read.