CVE-2021-37136
HIGHBzip2Decoder doesn't allow setting size restrictions for decompressed data
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
io.netty:netty-codec☕org.jboss.netty:netty☕io.netty:nettyReal-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
The Bzip2 decompression decoder function doesn't allow setting size restrictions on the decompressed output data (which affects the allocation size used during decompression). All users of Bzip2Decoder are affected. The malicious input can trigger an OOME and so a DoS attack
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | io.netty:netty-codec | all versions | 4.1.68.Final |
| ☕Maven | org.jboss.netty:netty | all versions | No fix |
| ☕Maven | io.netty:netty | all versions | No fix |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.netty:netty-codec. 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 io.netty:netty-codec to 4.1.68.Final or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-37136 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-2021-37136 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-2021-37136. 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-2021-37136 in your dependencies?
O3 detects CVE-2021-37136 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.