HIGH

CVE-2026-56853

CVSS v3

7.5

HIGH

EPSS Score

0.6 %

exploit probability, as of 2026-10-19

CISA KEV

known exploited

Exploitation

—

SSVC status

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Affected and fixed versions

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

golangBitnamiall versions · fixed in 1.25.13
stdlibGoall versions · fixed in 1.25.13
aardvark-dnsAlmaLinux:8all versions · fixed in 2:1.10.1-2.module_el8.10.0+3901+4b80ecd7
buildahAlmaLinux:10all versions · fixed in 2:1.43.1-6.el10_2and 1 other package
buildahAlmaLinux:9all versions · fixed in 2:1.43.3-2.el9_8and 1 other package
buildahAlmaLinux:8all versions · fixed in 2:1.33.14-6.module_el8.10.0+4269+94686149and 1 other package
cockpit-podmanAlmaLinux:8all versions · fixed in 84.1-1.module_el8.10.0+4102+6c76e544
conmonAlmaLinux:8all versions · fixed in 3:2.1.10-1.module_el8.10.0+3845+87b84552

41 more package ranges on OSV.dev

Vendor advisories

CVE-2026-56853 Red Hat Product Security2,778 products fixed · 244 known affected
net/http: golang: Go net/http: Unencrypted HTTP/2 connections vulnerable to Denial of Service
rhai/assisted-installer-rhel9 as a component of Assisted Installer for Red Hat OpenShift Container Platform 2 · albo/aws-load-balancer-operator as a component of AWS Load Balancer Operator · cert-manager/cert-manager-operator-rhel9 as a component of cert-manager Operator for Red Hat OpenShift
RHSA-2026:84734 Red Hat Product Security136 products fixed
Red Hat Security Advisory: RHOAI 3.4.5 - Red Hat OpenShift AI
RHSA-2026:83013 Red Hat Product Security8 products fixed
Red Hat Security Advisory: Logging for Red Hat OpenShift - 6.0.17
RHSA-2026:82315 Red Hat Product Security2 products fixed
Red Hat Security Advisory: Migration Toolkit for Applications
RHSA-2026:80684 Red Hat Product Security1 product fixed
Red Hat Security Advisory: Updated Red Hat OpenStack Platform 17.1 director Operator container images
RHSA-2026:77899 Red Hat Product Security1 product fixed
Red Hat Security Advisory: Red Hat Web Terminal Operator 1.11.2 release.

133 more advisories

Full record on NVD

Description

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.

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Published: 2026-08-13
Last Modified: 2026-08-14

Frequently asked questions

What is CVE-2026-56853?

Is CVE-2026-56853 actively exploited?

Active exploitation of CVE-2026-56853 has not been confirmed. Its EPSS score was 0.6% on 2026-10-19, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-56853?

CVE-2026-56853 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

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