HAProxy known bugs for maintenance branch 2.6 :  0 

This is maintenance branch 2.6 whose latest version is 2.6.35. If your version is not the last one in the maintenance branch, you are missing fixes for known bugs, and by not updating you are needlessly taking the responsibility for the risk of unexpected service outages and exposing your web site to possible security issues.

The HAProxy development team takes a great care of maintaining stable versions so that all users can apply bug fixes without having to take the risk of upgrading to a new branch. In turn users are expected to apply the fixes when the development team estimates that they were worth being backported to stable branches. In short, if you are running any 2.6 version other than 2.6.35, you're running with known bugs.

Quick links

Versions available in this branch

This branch contains the following releases :

DateVersionComment
2026-10-142.6.35 ⇐ last
2026-09-242.6.34 
2026-08-272.6.33 
2026-07-292.6.32 
2026-07-032.6.31 
2026-06-262.6.30 
2026-05-112.6.29 
2026-05-062.6.28 
2026-04-302.6.27 
2026-04-232.6.26 
2026-03-202.6.25 
2026-03-092.6.24 
2025-10-032.6.23 
2025-04-222.6.22 
2025-01-292.6.21 
2024-11-082.6.20 
2024-09-192.6.19 
2024-06-182.6.18 
2024-04-052.6.17 
2023-12-132.6.16 
2023-08-092.6.15 
2023-06-092.6.14 
2023-05-022.6.13 
2023-03-282.6.12 
2023-03-172.6.11 
2023-03-102.6.10 
2023-02-142.6.9 
2023-01-242.6.8 
2022-12-022.6.7 
2022-09-222.6.6 
2022-09-032.6.5 
2022-08-222.6.4 
2022-08-192.6.3 
2022-07-222.6.2 
2022-06-212.6.1 
2022-05-312.6.0 

Fixes for known bugs pending in this branch since the last release (2.6.35)

These fixes have already been queued for the next 2.6 release but no version was released with them yet. Note that fixes are backported several at a time from the development branch to maintenance branches, and the absence of a fix here doesn't mean none will be issued soon.

Bugs are almost always tagged with a severity (some people forget the severity tag when the bug is minor). The following severities are used :

Total known bugs in the latest version of this branch by category :

TotalCRITICALMAJORMEDIUMMINOR
0 0 0 0 0

Click on the subjects below to get the full description of the bug :

Merge dateSubject - Severity (minor, medium, major, critical)

Known bugs fixed in the development branch after the last commit in this branch

It is important to understand that not all of these commits are necessarily relevant to this version, but clicking on them will show the bug description. All fixes are made first in the development branch and then backported to the maintenance branches. This ensures no fix is lost when upgrading. If a fix was marked for backporting to this branch and is not there yet, it's likely that it is still missing. Do not hesitate to ask on the haproxy mailing list if you feel like a fix has been skipped.

DateSubject
2026-10-19BUG/MEDIUM: bwlim: never burst more than the pending data in input
2026-10-19BUG/MINOR: filters: free the error message of the filter-config parsers
2026-10-19BUG/MEDIUM: h3: split absolute URIs like the HTTP analysers do on output
2026-10-19BUG/MAJOR: mux-h2: split absolute URIs like the HTTP analysers do on output
2026-10-19BUG/MAJOR: mux-quic: do not crash on connection error after glitch threshold
2026-10-19BUG/MEDIUM: resolvers: reject too long labels when encoding a name
2026-10-18BUG/MINOR: sym: don't crash on images linked at a fixed base
2026-10-16BUG/MINOR: mux-h1: Don't subscribe for receives once read0 or error received
2026-10-16BUG/MEDIUM: mux-h1: don't spread-close idle conns with idle-close-on-response
2026-10-16BUG/MINOR: mux-h1: don't forward request trailers named like server name header
2026-10-16BUG/MINOR: mux-h1: search the websocket key in the right message
2026-10-16BUG/MINOR: mux-h1: only rely on the client's method for bodyless responses
2026-10-16BUG/MEDIUM: h1: reject absolute http(s) URIs with an empty host
2026-10-16BUG/MINOR: mux-h1: convert the argument of h1-case-adjust to lower case
2026-10-16BUG/MEDIUM: mux-h1: don't send chunked responses to HTTP/1.0 clients
2026-10-16BUG/MINOR: h1: forget a previous pass' results when parsing headers only
2026-10-16BUG/MINOR: h1: reject CONNECT authorities with an empty host
2026-10-16BUG/MEDIUM: h1: build a missing Host header from the authority of the URI
2026-10-16BUG/MEDIUM: mux-h1: don't lose error responses once a content-length was parsed
2026-10-16BUG/MINOR: mux-h1: report payload parsing glitches to the session
2026-10-16BUG/MEDIUM: mux-h1: don't swap buffers when transferring data with a reserved offset
2026-10-16BUG/MINOR: mux-h1: don't report a 408 error on timeout of a closed connection
2026-10-16BUG/MINOR: mux-h1: don't keep fast-forwarding disabled for the next streams
2026-10-16BUG/MINOR: mux-h1: reset the content-length/chunking state after a 1xx response
2026-10-16BUG/MEDIUM: mux-h1: don't stall when draining more than a buffer of data
2026-10-16BUG/MEDIUM: mux-h1: don't lose the end of the previous chunk in h1_make_chunk()
2026-10-16BUG/MEDIUM: h1: reject CONNECT request targets other than "host:port"
2026-10-16BUG/MINOR: mux-h1: don't dereference a NULL opposite sedesc in h1_fastfwd()
2026-10-16BUG/MINOR: mux-h1: wake the connection up when a pending error can be sent
2026-10-16BUG/MINOR: mux-h1: fix the open streams counter on stream creation failure
2026-10-16BUG/MINOR: mux-h1: only reset the session's timing info on the frontend side
2026-10-16BUG/MINOR: h1: don't use uninitialized start line pointers when restarting
2026-10-16BUG/MEDIUM: mux-h1: don't truncate responses on soft-stop
2026-10-16BUG/MEDIUM: mux-h1: don't truncate the response when closing after draining
2026-10-16BUG/MEDIUM: h1-htx: don't stall on messages ending exactly at the buffer's end
2026-10-16BUG/MEDIUM: h1: don't rewrite the Upgrade header when not cleaning headers
2026-10-16BUG/MINOR: h1: keep accepting unsafe violations after a parser reset
2026-10-16BUG/MEDIUM: h1: make the Connection/Upgrade headers cleanup idempotent
2026-10-16BUG/MEDIUM: mux-h1: Don't close the connection on a payload parsing error
2026-10-16BUG/MINOR: filters: fix silent compression disable with legacy "filter compression" first
2026-10-16BUG/MEDIUM: cli: Fix parsing of big payloads with dynamically allocated buffer
2026-10-16BUG/MINOR: quic: valid NEW_TOKEN connections are counted as half-open
2026-10-16BUG/MEDIUM: peers: keep the earliest sync task deadline
2026-10-16BUG/MINOR: mux_quic: do not crash on SE_SHR_DRAIN shut
2026-10-16BUG/MINOR: check: do not inspect errno if conn FDLESS
2026-10-16BUG/MINOR: mux_quic: prevent RS/SS on unistream with hq-interop
2026-10-16BUG/MEDIUM: mux_quic: prevent uaf on fctl frame after send error
2026-10-16BUG/MINOR: quic: handle EINTR on emission of packets without connection
2026-10-16BUG/MINOR: quic: use datagram destination as source for version negotiation
2026-10-16BUG/MINOR: quic: use datagram destination as source for stateless reset
2026-10-16BUG/MEDIUM: quic: use datagram destination as source for Retry
2026-10-15BUG/MINOR: quic: rearm packet on packet received even non ack-eliciting
2026-10-15BUG/MEDIUM: stats-file: shm-stats-file be counters not working anymore
2026-10-14BUG/MAJOR: h1-htx: report an error on a too long chunk-size line
2026-10-14BUG/MAJOR: mux-h2: properly handle short reads on PING frames

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