CVE-2026-65100Network attack vector

HTTP/2 header corruption via premature HPACK update

Published Jul 29, 2026 · Updated Jul 29, 2026

HPACK state desynchronization in Apache Traffic Server allows remote attackers to corrupt subsequent HTTP/2 header blocks after an encode failure. The HPACK encoder mutates its connection-scoped dynamic table before confirming that the current header block encoded successfully, so failure advances only the local state. Triggering an HTTP/2 encode failure requires no authentication or user interaction; later indexed header blocks can then be misinterpreted by the peer decoder.

CVSS severity4.8
Medium
EPSS probability0.35%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

HPACK state desynchronization in Apache Traffic Server allows remote attackers to corrupt subsequent HTTP/2 header blocks after an encode failure. The HPACK encoder mutates its connection-scoped dynamic table before confirming that the current header block encoded successfully, so failure advances only the local state. Triggering an HTTP/2 encode failure requires no authentication or user interaction; later indexed header blocks can then be misinterpreted by the peer decoder.

The record

CVE
CVE-2026-65100
Published
Jul 29, 2026
Updated
Jul 29, 2026
Vendor
The Apache Software Foundation
Product
Apache Traffic Server
Classifications
CWE-696
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 29, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 29, 2026Record 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 <=10.1.3
  2. Affected versionversion=8.0.0 <=8.1.9
  3. Affected versionversion=9.0.0 <=9.2.14

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Apache Software Foundation · Apache Traffic Serverversion=10.0.0 <=10.1.3; version=8.0.0 <=8.1.9; version=9.0.0 <=9.2.14

Published CVSS scores

4.8Apache Software FoundationCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:L
6.3Apache Software FoundationCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N

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-696Incorrect Behavior Order

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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