When a server is configured to support unencrypted HTTP/2, it reads a few bytes from each new connection to see if they contain the HTTP/2 client preface. ReadHeaderTimeout is unexpectedly not being applied when doing this.

There are packages installed that are affected by a vulnerability referenced in the following CVE:

  - When a server is configured to support unencrypted HTTP/2, it reads a few bytes from each new connection
    to see if they contain the HTTP/2 client preface. ReadHeaderTimeout is unexpectedly not being applied when
    doing this. (CVE-2026-56853)

The version of Golang running on the remote host is 1.25.x prior to 1.25.13, or 1.26.x prior to 1.26.6. It is, therefore, affected by multiple vulnerabilities in the standard library and the toolchain, as referenced in the golang-announce advisory.

  - The ToASCII and ToUnicode functions incorrectly accepted Punycode-encoded labels that decode to an     ASCII-only label. This can lead to privilege escalation in programs using the idna package.
    (CVE-2026-39821)

  - Parsing an invalid SVCB or HTTPS RR can panic when the size of a parameter value overflows the     message buffer in golang.org/x/net/dns/dnsmessage. (CVE-2026-46600)

  - When a server is configured to support unencrypted HTTP/2, it reads bytes from each new connection     to check for the HTTP/2 client preface. Previously this was done with no timeout. ReadHeaderTimeout     is now applied for this check. (CVE-2026-56853)

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - When a server is configured to support unencrypted HTTP/2, it reads a few bytes from each new connection     to see if they contain the HTTP/2 client preface. ReadHeaderTimeout is unexpectedly not being applied when     doing this. (CVE-2026-56853)

Note that Nessus relies on the presence of the package as reported by the vendor.

ID	Name	Product	Family	Type	Severity
445960	Golang: stdlib: security update to 1.25.13stdlib: security update to 1.26.6stdlib: security update to 1.27.0-rc.3	Tenable Cloud Security	Golang	Local	high
445960	Golang: stdlib: security update to 1.25.13stdlib: security update to 1.26.6stdlib: security update to 1.27.0-rc.3	Tenable Self-Hosted Container Security	Golang	Local	high
335411	Golang 1.25.x < 1.25.13 / 1.26.x < 1.26.6 Multiple Vulnerabilities	Nessus	Misc.	Local	critical
335359	Linux Distros Unpatched Vulnerability : CVE-2026-56853	Nessus	Misc.	Local	high

Detections

Analytics

CVE-2026-56853

high

Tenable Plugins

high

high

critical

high