CVE-2026-35356 is a medium-severity (CVSS 6.3) CWE-367 vulnerability in uu_install. O3 Security confirms whether CVE-2026-35356 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
uutils coreutils install Arbitrary File Overwrite with -D via Path Component Symlink Race
Real-World Exposure
uu_installReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.
Description
A Time-of-Check to Time-of-Use (TOCTOU) vulnerability exists in the install utility of uutils coreutils when using the -D flag. The command creates parent directories and subsequently performs a second path resolution to create the target file, neither of which is anchored to a directory file descriptor. An attacker with concurrent write access can replace a path component with a symbolic link between these operations, redirecting the privileged write to an arbitrary file system location.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | uu_install | all versions | 0.7.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for uu_install. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update uu_install to 0.7.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-35356 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-35356 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-35356. 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-2026-35356 in your dependencies?
O3 detects CVE-2026-35356 across crates.io dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.