CVE-2026-33555
5.8
MEDIUM
CVSS 3.1
EPSS 0.30%
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.
How to fix CVE-2026-33555
To remediate CVE-2026-33555, upgrade the affected package to a fixed version below.
- —upgrade to 3.3.6 or later
Is CVE-2026-33555 being exploited?
Low — EPSS is 0.3%, meaning exploitation activity has not been observed at scale.
Affected packages (1)
- >= 2.6.0, < 3.3.6
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | MEDIUM5.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N |