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HIGH

CVE-2026-90678

CVSS v3

7.5

HIGH

EPSS Score

0.8 %

exploit probability, as of 2026-09-28

CISA KEV

No

known exploited

Exploitation

—

SSVC status

Description

An issue was discovered in HAProxy 3.3.0 through 3.4.4 and in 3.5-dev1 through 3.5-dev5. Exploitation requires an HTTP/3 frontend: HAProxy must be built with QUIC support and configured with a QUIC bind listener, and the affected traffic must reach a backend over HTTP/1.1 using chunked transfer coding on a reused connection. Under those conditions, when an HTTP/3 request carries no Content-Length header, the HTTP/3 multiplexer credits the length declared in a DATA frame header to the stream endp

Technical details

Published
2026-09-13
Last Modified
2026-09-13

Frequently asked questions

What is CVE-2026-90678?

An issue was discovered in HAProxy 3.3.0 through 3.4.4 and in 3.5-dev1 through 3.5-dev5. Exploitation requires an HTTP/3 frontend: HAProxy must be built with QUIC support and configured with a QUIC bind listener, and the affected traffic must reach a backend over HTTP/1.1 using chunked transfer coding on a reused connection. Under those conditions, when an HTTP/3 request carries no Content-Length header, the HTTP/3 multiplexer credits the length declared in a DATA frame header to the stream endp

Is CVE-2026-90678 actively exploited?

Active exploitation of CVE-2026-90678 has not been confirmed. Its EPSS score was 0.8% on 2026-09-28, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-90678?

CVE-2026-90678 has a CVSS v3 base score of 7.5 (HIGH severity).

Is CVE-2026-90678 affecting your environment?

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