CVE-2023-39456Network attack vector

Unauthenticated service abort via malformed HTTP/2 frames

Published Oct 17, 2023 · Updated Jun 12, 2025

Improper input validation in Apache Traffic Server 9.0.0 through 9.2.2 allows remote attackers to abort the proxy with malformed HTTP/2 frames. Apache has not disclosed which HTTP/2 frame field or parser operation mishandles the malformed input before the process aborts. An unauthenticated client must reach an HTTP/2 listener; successful exploitation crashes the proxy without reported data disclosure or modification.

CVSS severity7.5
High
EPSS probability53.76%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in Apache Traffic Server 9.0.0 through 9.2.2 allows remote attackers to abort the proxy with malformed HTTP/2 frames. Apache has not disclosed which HTTP/2 frame field or parser operation mishandles the malformed input before the process aborts. An unauthenticated client must reach an HTTP/2 listener; successful exploitation crashes the proxy without reported data disclosure or modification.

The record

CVE
CVE-2023-39456
Published
Oct 17, 2023
Updated
Jun 12, 2025
Vendor
The Apache Software Foundation
Product
Apache Traffic Server
Classifications
CWE-20, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 17, 2023CVE publishedPublication date reported by the CVE source.
  2. Jun 12, 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=0 <=9.2.2
  2. Affected versionversion=9.0.0 <=9.2.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Apache Software Foundation · Apache Traffic Serverversion=0 <=9.2.2; version=9.0.0 <=9.2.2

Published CVSS scores

7.5CISA-ADPCVSS: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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation
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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