CVE-2026-56866

Publication date 8 October 2026

Last updated 19 October 2026

Ubuntu priority

Medium

Why this priority?

Cvss 3 Severity Score

7.5 · High

Score breakdown

Description

When http.Transport sends an HTTP/1 CONNECT request with a non-empty Request.Body, it writes the body directly to the connection without framing after the request headers. If the server rejects the CONNECT request with a non-2xx keep-alive response, Transport returns the connection to the idle pool. Because CONNECT requests do not have a request body, the server may interpret the trailing body bytes as a subsequent pipelined HTTP/1.1 request on the connection, leaving the pooled connection desynchronized and causing the next caller that reuses it to read the response to the injected request. In reverse proxies (including httputil.ReverseProxy) that forward CONNECT requests through a shared Transport, this can lead to cross-user response poisoning.

Read the notes from the security team

Status

Package Ubuntu Release Status
golang 26.10 stonking Not in release
26.04 LTS resolute Not in release
24.04 LTS noble Not in release
22.04 LTS jammy Not in release
golang-1.6 26.10 stonking Not in release
26.04 LTS resolute Not in release
24.04 LTS noble Not in release
22.04 LTS jammy Not in release
16.04 LTS xenial
Needs evaluation
golang-1.8 26.10 stonking Not in release
26.04 LTS resolute Not in release
24.04 LTS noble Not in release
22.04 LTS jammy Not in release
18.04 LTS bionic
Needs evaluation
golang-1.9 26.10 stonking Not in release
26.04 LTS resolute Not in release
24.04 LTS noble Not in release
22.04 LTS jammy Not in release
18.04 LTS bionic
Needs evaluation
golang-1.10 26.10 stonking Not in release
26.04 LTS resolute Not in release
24.04 LTS noble Not in release
22.04 LTS jammy Not in release
18.04 LTS bionic
Needs evaluation
16.04 LTS xenial
Needs evaluation
14.04 LTS trusty
Needs evaluation
golang-1.13 26.10 stonking Not in release
26.04 LTS resolute Not in release
24.04 LTS noble Not in release
22.04 LTS jammy
Needs evaluation
20.04 LTS focal
Needs evaluation
18.04 LTS bionic
Needs evaluation
16.04 LTS xenial
Needs evaluation
golang-1.14 26.10 stonking Not in release
26.04 LTS resolute Not in release
24.04 LTS noble Not in release
22.04 LTS jammy Not in release
20.04 LTS focal
Needs evaluation
golang-1.16 26.10 stonking Not in release
26.04 LTS resolute Not in release
24.04 LTS noble Not in release
22.04 LTS jammy Not in release
20.04 LTS focal
Needs evaluation
18.04 LTS bionic
Needs evaluation
golang-1.17 26.10 stonking Not in release
26.04 LTS resolute Not in release
24.04 LTS noble Not in release
22.04 LTS jammy
Needs evaluation
golang-1.18 26.10 stonking Not in release
26.04 LTS resolute Not in release
24.04 LTS noble Not in release
22.04 LTS jammy
Needs evaluation
20.04 LTS focal
Needs evaluation
18.04 LTS bionic
Needs evaluation
16.04 LTS xenial
Needs evaluation
golang-1.20 26.10 stonking Not in release
26.04 LTS resolute Not in release
24.04 LTS noble Not in release
22.04 LTS jammy
Needs evaluation
20.04 LTS focal
Needs evaluation
golang-1.21 26.10 stonking Not in release
26.04 LTS resolute Not in release
24.04 LTS noble
Needs evaluation
22.04 LTS jammy
Needs evaluation
20.04 LTS focal
Needs evaluation
golang-1.22 26.10 stonking Not in release
26.04 LTS resolute Not in release
24.04 LTS noble
Fixed in 1.22.2-2ubuntu0.5
22.04 LTS jammy
Fixed in 1.22.2-2~22.04.4
20.04 LTS focal
Fixed in 1.22.2-2~20.04.3
golang-1.23 26.10 stonking Not in release
26.04 LTS resolute
Needs evaluation
24.04 LTS noble
Needs evaluation
22.04 LTS jammy
Needs evaluation
golang-1.24 26.10 stonking Not in release
26.04 LTS resolute
Needs evaluation
24.04 LTS noble
Needs evaluation
22.04 LTS jammy
Needs evaluation
golang-1.25 26.10 stonking Not in release
26.04 LTS resolute
Needs evaluation
24.04 LTS noble
Needs evaluation
22.04 LTS jammy
Needs evaluation
golang-1.26 26.10 stonking
Needs evaluation
26.04 LTS resolute
Needs evaluation
24.04 LTS noble
Needs evaluation
22.04 LTS jammy
Needs evaluation
golang-1.27 26.10 stonking
Needs evaluation
26.04 LTS resolute Not in release
24.04 LTS noble Not in release
22.04 LTS jammy Not in release

Get expanded security coverage with Ubuntu Pro

Reduce your average CVE exposure time from 98 days to 1 day with expanded CVE patching, ten-years security maintenance and optional support for the full stack of open-source applications. Free for personal use.

Get Ubuntu Pro 30-day free trial

Notes

mdeslaur

Packages built using golang need to be rebuilt once the vulnerability has been fixed. This CVE entry does not list packages that need rebuilding outside of the main repository or the Ubuntu variants with PPA overlays. Warning: do not include nullboot in the list of no-change rebuilds after fixing an issue in golang.

Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package Patch details
golang-1.22

Severity score breakdown

CVSS version: CVSS v3.0

Base score 7.5 · High

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

References

Related Ubuntu Security Notices (USN)

Other references

Access our resources on patching vulnerabilities