Upstream information
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 endpoint's known-input-payload estimate at the moment the frame header is decoded, before the payload has been received, and that declared length is emitted verbatim as the HTTP/1.1 chunk size. A remote unauthenticated client that declares more payload than it delivers and then ends the stream causes HAProxy to announce a chunk larger than the bytes it writes and to return the connection to the idle pool in a desynchronized state. The result is potential HTTP request smuggling on reused backend connections: an attacker can place a request past a frontend rule such as a path-based http-request deny, so that the smuggled request is never seen by HAProxy's HTTP analysis, and can cause concurrent clients' requests, including their request lines and Authorization headers, to be consumed as the attacker's request body and lost. Exploitation is not deterministic; it depends on a race with backend connection pooling, succeeding in a majority of but not all trials during testing, and can be retried freely. The mechanism was introduced in 3.3-dev10; releases 3.2.x and earlier are unaffected.SUSE information
Overall state of this security issue: Resolved
This issue is currently rated as having important severity.
| CVSS detail | CNA (MITRE) | SUSE |
|---|---|---|
| Base Score | 7.5 | 7.5 |
| Vector | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:L | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:L |
| Attack Vector | Network | Network |
| Attack Complexity | High | High |
| Privileges Required | None | None |
| User Interaction | None | None |
| Scope | Changed | Changed |
| Confidentiality Impact | None | None |
| Integrity Impact | High | High |
| Availability Impact | Low | Low |
| CVSSv3 Version | 3.1 | 3.1 |
Status of this issue by product and package
Please note that this evaluation state might be work in progress, incomplete or outdated. Also information for service packs in the LTSS phase is only included for issues meeting the LTSS criteria. If in doubt, feel free to contact us for clarification. The updates are grouped by state of their lifecycle. SUSE product lifecycles are documented on the lifecycle page.
| Product(s) | Source package | State |
|---|---|---|
| Products under general support and receiving all security fixes. | ||
| SUSE Linux Enterprise High Availability Extension 15 SP7 | haproxy | Not affected |
| SUSE Linux Enterprise High Availability Extension 16.0 | haproxy | Not affected |
| SUSE Linux Enterprise Micro 5.3 | haproxy | Not affected |
| SUSE Linux Enterprise Micro 5.4 | haproxy | Not affected |
| SUSE Linux Enterprise Micro 5.5 | haproxy | Not affected |
| SUSE Linux Enterprise Server 16.1 | haproxy | Not affected |
| SUSE Linux Enterprise Server for SAP applications 16.0 | haproxy | Not affected |
| SUSE Linux Enterprise Server for SAP applications 16.1 | haproxy | Not affected |
| SUSE Linux Micro 6.0 | haproxy | Not affected |
| SUSE Linux Micro 6.1 | haproxy | Not affected |
| SUSE Linux Micro 6.2 | haproxy | Not affected |
| openSUSE Leap 16.0 | haproxy | Not affected |
| Products under Long Term Service Pack support and receiving important and critical security fixes. | ||
| SUSE Linux Enterprise High Availability Extension 12 SP5 | haproxy | Not affected |
| SUSE Linux Enterprise High Availability Extension 15 SP4 | haproxy | Not affected |
| SUSE Linux Enterprise High Availability Extension 15 SP5 | haproxy | Not affected |
| SUSE Linux Enterprise Server for SAP Applications 12 SP5 | haproxy | Not affected |
| Products past their end of life and not receiving proactive updates anymore. | ||
| SUSE Linux Enterprise High Availability Extension 15 SP6 | haproxy | Not affected |
| openSUSE Leap 15.4 | haproxy | Not affected |
| openSUSE Leap 15.5 | haproxy | Not affected |
| openSUSE Leap 15.6 | haproxy | Not affected |
| openSUSE Leap Micro 5.3 | haproxy | Not affected |
| openSUSE Leap Micro 5.4 | haproxy | Not affected |
| openSUSE Leap Micro 5.5 | haproxy | Not affected |
SUSE Timeline for this CVE
CVE page created: Mon Sep 14 11:41:07 2026CVE page last modified: Tue Sep 15 15:46:02 2026