CVE-2026-35357
MEDIUMCVE-2026-35357 is a medium-severity (CVSS 4.7) CWE-367 vulnerability in uutils coreutils. O3 Security detects and blocks CVE-2026-35357 exploitation at runtime via eBPF exploit-chain detection and L7 egress monitoring, even on unpatched systems.
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…
Description
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 Products
coreutilsuutilsDetection & mitigation playbook
Vendor / applianceDetect
Inventory every uutils coreutils deployment and check each version against the affected-products list above. Because the exploit targets the running system rather than your application code, also watch for exploitation at the network and runtime layer — O3 flags the exploit behaviour from runtime telemetry and egress traffic even before a vulnerable build is confirmed.
Remediation status
No patch has shipped for CVE-2026-35357 yet — track the uutils coreutils advisory for a fixed release and apply the workarounds below in the meantime.
Mitigate without a patch
Cut exposure now: restrict the management/admin interface to trusted networks, segment the device, and apply the vendor's recommended configuration mitigations and any WAF/IPS signature. O3's runtime protection blocks the exploit chain at execution, holding the line on unpatched or end-of-life systems until you can patch.
How O3 protects you
O3 detects and blocks CVE-2026-35357 exploitation at runtime: eBPF exploit-chain detection, plus L7 egress monitoring that catches the post-exploitation callback and severs the attacker's outbound channel.
Tailored to CVE-2026-35357. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-35357 being exploited in your environment?
O3's eBPF runtime sensors and L7 egress monitoring detect and block the CVE-2026-35357 exploit chain at execution — protecting unpatched and end-of-life systems until the vendor patch is applied.