CVE-2021-28165Network attack vector

Remote CPU exhaustion via invalid TLS frame

Published Apr 1, 2021 · Updated Aug 27, 2025

Denial of service in Eclipse Jetty 7.2.2 through 9.4.38 allows remote attackers to interrupt service via a large invalid TLS frame. Jetty's TLS handling incorrectly processes frames larger than 17408 bytes on SSL/TLS HTTP/1.1, HTTP/2, or WebSocket connections, driving CPU usage to 100%; the unauthenticated network attack requires no user interaction and primarily causes service interruption.

CVSS severity7.5
High
EPSS probability53.86%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Eclipse Jetty 7.2.2 through 9.4.38 allows remote attackers to interrupt service via a large invalid TLS frame. Jetty's TLS handling incorrectly processes frames larger than 17408 bytes on SSL/TLS HTTP/1.1, HTTP/2, or WebSocket connections, driving CPU usage to 100%; the unauthenticated network attack requires no user interaction and primarily causes service interruption.

The record

CVE
CVE-2021-28165
Published
Apr 1, 2021
Updated
Aug 27, 2025
Vendor
The Eclipse Foundation
Product
Eclipse Jetty
Classifications
CWE-551, CWE-400, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 1, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 27, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=10.0.0.alpha0 <unspecified
  2. Affected versionversion=11.0.0.alpha0 <unspecified
  3. Affected versionversion=7.2.2 <unspecified
  4. Affected versionversion=unspecified <=10.0.1
  5. Affected versionversion=unspecified <=11.0.1
  6. Affected versionversion=unspecified <=9.4.38

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Eclipse Foundation · Eclipse Jettyversion=10.0.0.alpha0 <unspecified; version=11.0.0.alpha0 <unspecified; version=7.2.2 <unspecified; version=unspecified <=10.0.1; version=unspecified <=11.0.1; version=unspecified <=9.4.38

Published CVSS scores

7.5Eclipse Foundation CNACVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-551Incorrectly Implemented Security Check for Standard
CWE-400Uncontrolled Resource Consumption
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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