HTTP Request Smuggling Affecting golang-src package, versions <0:1.26.9-1.amzn2023.0.1


Severity

Recommended
high

Based on Amazon Linux security rating.

Threat Intelligence

EPSS
0.6% (50th percentile)

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  • Snyk IDSNYK-AMZN2023-GOLANGSRC-21700391
  • published25 Oct 2026
  • disclosed8 Oct 2026

Introduced: 8 Oct 2026

CVE-2026-56866  (opens in a new tab)
CWE-444  (opens in a new tab)

How to fix?

Upgrade Amazon-Linux:2023 golang-src to version 0:1.26.9-1.amzn2023.0.1 or higher.
This issue was patched in ALAS2023-2026-3225.

NVD Description

Note: Versions mentioned in the description apply only to the upstream golang-src package and not the golang-src package as distributed by Amazon-Linux. See How to fix? for Amazon-Linux:2023 relevant fixed versions and status.

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.

CVSS Base Scores

version 3.1