Is CVE-2026-33555 in the CISA KEV catalog?

No. CVE-2026-33555 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-33555?

CVE-2026-33555 has a CVSS v3 base score of 4.0 (Moderate).

What is the EPSS score for CVE-2026-33555?

CVE-2026-33555 has an EPSS score of 0.30% (21th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-33555?

Upgrade haproxy on debian 13 to 3.0.11-1+deb13u3 or later.

CVE & CISA-KEV Catalog

CVE-2026-33555

MEDIUM

4.0

CVSS v3

NVD

Description

An issue was discovered in HAProxy before 3.3.6. The HTTP/3 parser does not check that the received body length matches a previously announced content-length when the stream is closed via a frame with an empty payload. This can cause desynchronization issues with the backend server and could be used for request smuggling. The earliest affected version is 2.6.

CWE-130

How to fix

Remediation Available

haproxyDebian

Fixed in:3.0.11-1+deb13u3CVE-2026-33555

Fixed in:3.2.15-1CVE-2026-33555

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityHigh

Privileges RequiredNone

User InteractionNone

ScopeChanged

Impact

ConfidentialityNone

IntegrityLow

AvailabilityNone

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:N

Exploit Intelligence

0.30%probability of exploitation in 30 days

21stpercentile

Low risk: more likely to be exploited than 21% of all known CVEs.

References

Patch1

github.com

Exploit1

r3verii.github.io

Release Notes2

Product1

haproxy.org

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-06-29.