CVE-2026-33555
Description
A flaw was found in HAProxy. A remote attacker could exploit this vulnerability by sending a specially crafted HTTP/3 request. The HTTP/3 parser fails to verify that the received body length matches the announced content-length when a stream is closed with an empty payload. This desynchronization with the backend server can lead to request smuggling, allowing an attacker to bypass security mechanisms and potentially access unauthorized resources.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 4 | 5.8 | 4 |
| Attack Vector | Network | Network | Network |
| Attack Complexity | High | Low | High |
| Privileges Required | None | None | None |
| User Interaction | None | None | None |
| Scope | Changed | Changed | Changed |
| Confidentiality | None | None | None |
| Integrity Impact | Low | Low | Low |
| Availability Impact | None | None | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:N
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
cve.org: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:N
Understanding the Weakness (CWE)
Confidentiality,Integrity
Technical Impact: Read Memory; Modify Memory; Varies by Context
Frequently Asked Questions
Not sure what something means? Check out our Security Glossary.
Want to get errata notifications? Sign up here.
