CVE-2026-33555 (GCVE-0-2026-33555)

Vulnerability from cvelistv5 – Published: 2026-04-13 00:00 – Updated: 2026-04-22 18:43
VLAI?
Summary
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.
Severity ?
4 (Medium)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:N
CWE
  • CWE-130 - Improper Handling of Length Parameter Inconsistency
Assigner
References
Impacted products
Vendor Product Version
HAProxy HAProxy Affected: 2.6 , < 3.3.6 (custom)
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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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