CVE-2026-35373 is a low-severity (CVSS 3.3) CWE-176 vulnerability in uu_ln. O3 Security confirms whether CVE-2026-35373 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
ln: rejects non-UTF-8 source filenames in target-directory mode
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-35373.
Real-World Exposure
uu_lnReal-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
In target-directory forms (ln SOURCE... DIRECTORY), ln rejects source paths with non-UTF-8 filename bytes, while GNU accepts them. Breaks GNU compatibility for byte-oriented filenames on Unix filesystems.
PoC:
name=$(printf 'bad_\377'); mkdir dst; : > "$name"; ln "$name" dst
# GNU: exit 0, creates dst/bad_\377 ; uutils: exit 1, dst empty
Zellic private finding (zellic-ext/coreutils-private PR #84). Reported in the Zellic uutils coreutils Program Security Assessment (for Canonical, Jan 2026), audited commit 3a07ffc5a9bd4c283e75afa548ba1f1957bad242.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | uu_ln | all versions | 0.6.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for uu_ln. 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_ln to 0.6.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-35373 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-2026-35373 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-2026-35373. 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-2026-35373 in your dependencies?
O3 detects CVE-2026-35373 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.