CVE-2026-90678Network attack vectorHinoki check available

Request smuggling via premature HTTP/3 length accounting

Published Sep 13, 2026 · Updated Sep 13, 2026

HTTP request smuggling in HAProxy 3.3.0 through 3.4.4 and 3.5-dev1 through 3.5-dev5 allows remote attackers to bypass frontend rules. The HTTP/3 multiplexer credits a DATA frame's declared length before receiving its payload and emits that value unchanged as the HTTP/1.1 chunk size. Exploitation requires a QUIC-enabled frontend, a chunked HTTP/1.1 backend on a reused connection, and a favorable pooling race; another client's request and Authorization header can be consumed as body data.

CVSS severityUnavailable
Unscored
EPSS probability0.52%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

HTTP request smuggling in HAProxy 3.3.0 through 3.4.4 and 3.5-dev1 through 3.5-dev5 allows remote attackers to bypass frontend rules. The HTTP/3 multiplexer credits a DATA frame's declared length before receiving its payload and emits that value unchanged as the HTTP/1.1 chunk size. Exploitation requires a QUIC-enabled frontend, a chunked HTTP/1.1 backend on a reused connection, and a favorable pooling race; another client's request and Authorization header can be consumed as body data.

The record

CVE
CVE-2026-90678
Published
Sep 13, 2026
Updated
Sep 13, 2026
Vendor
HAProxy Technologies
Product
HAProxy
Classifications
T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 13, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 13, 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=3.3.0 <=3.3.14
  2. Affected versionversion=3.4.0 <=3.4.4
  3. Affected versionversion=3.5-dev1 <=3.5-dev5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

HAProxy Technologies · HAProxyversion=3.3.0 <=3.3.14; version=3.4.0 <=3.4.4; version=3.5-dev1 <=3.5-dev5

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.

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

T1190Exploit Public-Facing Application

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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