CVE-2021-35516
HIGHCVE-2021-35516 is a high-severity (CVSS 7.5) CWE-130 vulnerability in org.apache.commons:commons-compress. 1 public exploit reference exists, so weaponization risk is real. O3 Security confirms whether CVE-2021-35516 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Improper Handling of Length Parameter Inconsistency in Compress
Blast Radius
org.apache.commons:commons-compressReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
When reading a specially crafted 7Z archive, Compress can be made to allocate large amounts of memory that finally leads to an out of memory error even for very small inputs. This could be used to mount a denial of service attack against services that use Compress' sevenz package.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.apache.commons:commons-compress | all versions | 1.21 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.apache.commons:commons-compress. 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 org.apache.commons:commons-compress to 1.21 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-35516 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-2021-35516 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-2021-35516. 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-2021-35516 in your dependencies?
O3 detects CVE-2021-35516 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.