CVE-2026-40931
HIGHCVE-2026-40931 is a high-severity (CVSS 8.4) vulnerability in compressing. O3 Security confirms whether CVE-2026-40931 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Complete Bypass of CVE-2026-24884 Patch via Git-Delivered Symlink Poisoning in compressing
Real-World Exposure
compressing📦compressingReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects npm packages — download data is not available via public APIs for these ecosystems.
Description
Compressing is a compressing and uncompressing lib for node. Prior to 2.1.1 and 1.10.5, the patch for CVE-2026-24884 relies on a purely logical string validation within the isPathWithinParent utility. This check verifies if a resolved path string starts with the destination directory string but fails to account for the actual filesystem state. By exploiting this "Logical vs. Physical" divergence, an attacker can bypass the security check using a Directory Poisoning technique (pre-existing symbolic links). This vulnerability is fixed in 2.1.1 and 1.10.5.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | compressing | ≥ 2.0.0&&< 2.1.1 | 2.1.1 |
| 📦npm | compressing | all versions | 1.10.5 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for compressing. 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 compressing to 2.1.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-40931 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-2026-40931 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-2026-40931. 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-2026-40931 in your dependencies?
O3 detects CVE-2026-40931 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.