CVE-2026-77762Network attack vectorHinoki check available

Cross-request trailer injection via stale HPACK emitter

Published Sep 23, 2026 · Updated Sep 23, 2026

Race condition in HTTP/2 processing in affected Apache Tomcat releases allows remote attackers to inject trailers into another request. During stream replacement, HpackDecoder retains a stale HeaderEmitter reference and emits decoded trailer fields into a recycled pooled Request. Triggering the flaw requires concurrent HTTP/2 request processing and timing-dependent stream replacement; the consequence is cross-request metadata injection.

CVSS severityUnavailable
Unscored
EPSS probability0.36%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Race condition in HTTP/2 processing in affected Apache Tomcat releases allows remote attackers to inject trailers into another request. During stream replacement, HpackDecoder retains a stale HeaderEmitter reference and emits decoded trailer fields into a recycled pooled Request. Triggering the flaw requires concurrent HTTP/2 request processing and timing-dependent stream replacement; the consequence is cross-request metadata injection.

The record

CVE
CVE-2026-77762
Published
Sep 23, 2026
Updated
Sep 23, 2026
Vendor
The Apache Software Foundation
Product
Apache Tomcat
Classifications
CWE-362, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 23, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 23, 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=10.1.0-M1 <=10.1.59
  2. Affected versionversion=11.0.0-M1 <=11.0.25
  3. Affected versionversion=8.56.59 <=8.5.100
  4. Affected versionversion=9.0.39 <=9.0.121

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Apache Software Foundation · Apache Tomcatversion=10.1.0-M1 <=10.1.59; version=11.0.0-M1 <=11.0.25; version=8.56.59 <=8.5.100; version=9.0.39 <=9.0.121

Published CVSS scores

No CVSS assessment is available in this record.

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.

Activity data is delayed. The latest report is Sep 28, 2026.

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

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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