How severe is CVE-2021-28165?

CVE-2021-28165 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2021-28165?

CVE-2021-28165 affects the following packages: org.eclipse.jetty:jetty-server (Maven), org.eclipse.jetty:jetty-server (Maven), org.eclipse.jetty:jetty-server (Maven). Ecosystems affected: Maven.

How do I fix CVE-2021-28165?

Update org.eclipse.jetty:jetty-server to 9.4.39 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-28165 is resolved across your whole dependency graph.

How do I detect CVE-2021-28165 in my Maven dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.eclipse.jetty:jetty-server. 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.

How do I mitigate CVE-2021-28165 if there is no patch (or I can't update yet)?

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 does O3 Security protect against CVE-2021-28165?

O3 pinpoints whether CVE-2021-28165 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is CVE-2021-28165 actively exploited in the wild?

Yes. There are 1 known exploit references for CVE-2021-28165, including 1 in-the-wild exploitation observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What type of vulnerability is CVE-2021-28165?

CVE-2021-28165 is classified as Uncontrolled Resource Consumption (CWE-400), CWE-551 (CWE-551), CWE-755 (CWE-755). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2021-28165 published, and has it been updated?

CVE-2021-28165 was published on April 1, 2021 and was last updated on July 8, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕ Maven

CVE-2021-28165

HIGH

Jetty vulnerable to incorrect handling of invalid large TLS frame, exhausting CPU resources

Also known asBIT-jenkins-2021-28165GHSA-26vr-8j45-3r4w

Published

Apr 1, 2021

Updated

Jul 8, 2026

Affected

3 pkgs

Patched

3 / 3

Exploits

1 known

Blast Radius

3 pkgs affected

☕org.eclipse.jetty:jetty-server☕org.eclipse.jetty:jetty-server☕org.eclipse.jetty:jetty-server

Real-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

In Eclipse Jetty 7.2.2 to 9.4.38, 10.0.0.alpha0 to 10.0.1, and 11.0.0.alpha0 to 11.0.1, CPU usage can reach 100% upon receiving a large invalid TLS frame.

Affected Packages

3 total 3 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`org.eclipse.jetty:jetty-server`	≥ 7.2.2&&< 9.4.39	9.4.39
☕Maven	`org.eclipse.jetty:jetty-server`	≥ 10.0.0&&< 10.0.2	10.0.2
☕Maven	`org.eclipse.jetty:jetty-server`	≥ 11.0.0&&< 11.0.2	11.0.2

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

In Eclipse Jetty 7.2.2 to 9.4.38, 10.0.0.alpha0 to 10.0.1, and 11.0.0.al…

github.comNVDAug 2021

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.eclipse.jetty:jetty-server. 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.eclipse.jetty:jetty-server to 9.4.39 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-28165 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-2021-28165 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-2021-28165. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

In Eclipse Jetty 7.2.2 to 9.4.38, 10.0.0.alpha0 to 10.0.1, and 11.0.0.alpha0 to 11.0.1, CPU usage can reach 100% upon receiving a large invalid TLS frame.

O3 Security · Impact-Aware SCA

Is CVE-2021-28165 in your dependencies?

O3 detects CVE-2021-28165 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my dependencies How O3 SCA works