CVE-2026-21441Network attack vectorHinoki check available

Client resource exhaustion via decoded redirect draining

Published Jan 7, 2026 · Updated Aug 28, 2026

Resource exhaustion in urllib3 1.22 through 2.6.2 allows remote attackers to consume client CPU and memory via compressed redirects. HTTPResponse.drain_conn reads an unread redirect body with decoding enabled, so compressed data is fully expanded before application reads and outside configured read limits. Exploitation requires streaming untrusted content with preload_content=False while redirects remain enabled; the resulting resource pressure can hang or crash the client process.

CVSS severity8.9
High
EPSS probability2.96%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Resource exhaustion in urllib3 1.22 through 2.6.2 allows remote attackers to consume client CPU and memory via compressed redirects. HTTPResponse.drain_conn reads an unread redirect body with decoding enabled, so compressed data is fully expanded before application reads and outside configured read limits. Exploitation requires streaming untrusted content with preload_content=False while redirects remain enabled; the resulting resource pressure can hang or crash the client process.

The record

CVE
CVE-2026-21441
Published
Jan 7, 2026
Updated
Aug 28, 2026
Vendor
389 Directory Server
Product
Red Hat Quay
Classifications
CWE-409, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 7, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 28, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Affected versions are unavailable in this record. Check the vendor advisory for version and patch details.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

389 Directory Server · Red Hat QuayAffected versions are unavailable in this record.
389 Directory Server · Red Hat OpenShift ServerlessAffected versions are unavailable in this record.
389 Directory Server · Red Hat Ansible Automation Platform Ansible CoreAffected versions are unavailable in this record.
389 Directory Server · Red Hat OpenShift LightspeedAffected versions are unavailable in this record.
389 Directory Server · cert-manager Operator for Red Hat OpenShiftAffected versions are unavailable in this record.
389 Directory Server · Red Hat OpenShift AIAffected versions are unavailable in this record.
389 Directory Server · OpenShift API for Data ProtectionAffected versions are unavailable in this record.
389 Directory Server · Mirror Registry for Red Hat OpenShiftAffected versions are unavailable in this record.
389 Directory Server · Red Hat Edge ManagerAffected versions are unavailable in this record.
389 Directory Server · Red Hat OpenShift Dev SpacesAffected versions are unavailable in this record.
389 Directory Server · OpenShift Developer Tools and ServicesAffected versions are unavailable in this record.
389 Directory Server · Red Hat Ceph StorageAffected versions are unavailable in this record.
389 Directory Server · Red Hat Developer HubAffected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux Update Services for SAP SolutionsAffected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux AIAffected versions are unavailable in this record.
389 Directory Server · Red Hat OpenShift Data FoundationAffected versions are unavailable in this record.
389 Directory Server · Zero Trust Workload Identity Manager - Tech PreviewAffected versions are unavailable in this record.
389 Directory Server · Red Hat Advanced Cluster Management for KubernetesAffected versions are unavailable in this record.
389 Directory Server · Red Hat Advanced Cluster Security for KubernetesAffected versions are unavailable in this record.
389 Directory Server · Multicluster Global HubAffected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 8.8 Update Services for SAP SolutionsAffected versions are unavailable in this record.
389 Directory Server · Red Hat Migration Toolkit for ContainersAffected versions are unavailable in this record.
389 Directory Server · External Secrets Operator for Red Hat OpenShiftAffected versions are unavailable in this record.
389 Directory Server · Red Hat Ansible Automation PlatformAffected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 10Affected versions are unavailable in this record.
389 Directory Server · Migration Toolkit for ContainersAffected versions are unavailable in this record.
389 Directory Server · Red Hat Update Infrastructure 5Affected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 9.2 Update Services for SAP SolutionsAffected versions are unavailable in this record.
389 Directory Server · Red Hat Ceph Storage 9Affected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 9.4 Extended Update SupportAffected versions are unavailable in this record.
389 Directory Server · Multiarch Tuning OperatorAffected versions are unavailable in this record.
389 Directory Server · Migration Toolkit for VirtualizationAffected versions are unavailable in this record.
389 Directory Server · Red Hat Connectivity LinkAffected versions are unavailable in this record.
389 Directory Server · Red Hat OpenStack PlatformAffected versions are unavailable in this record.
urllib3 · urllib3version=>= 1.22, < 2.6.3
389 Directory Server · Red Hat OpenShift GitOpsAffected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux Telecommunications Update ServiceAffected versions are unavailable in this record.
389 Directory Server · Network ObservabilityAffected versions are unavailable in this record.
389 Directory Server · Red Hat Certification Program for Red Hat Enterprise Linux 9Affected versions are unavailable in this record.
389 Directory Server · Red Hat AI Inference Server 3.2Affected versions are unavailable in this record.
389 Directory Server · Zero Trust Workload Identity ManagerAffected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update SupportAffected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-OnAffected versions are unavailable in this record.
389 Directory Server · Red Hat Discovery 2Affected versions are unavailable in this record.
389 Directory Server · Red Hat SatelliteAffected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 8.2 Advanced Update SupportAffected versions are unavailable in this record.
389 Directory Server · Red Hat Update InfrastructureAffected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 9Affected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 9.0 Update Services for SAP SolutionsAffected versions are unavailable in this record.
389 Directory Server · Red Hat OpenShift PipelinesAffected versions are unavailable in this record.
389 Directory Server · multicluster engine for KubernetesAffected versions are unavailable in this record.
389 Directory Server · Red Hat OpenShift Container Platform 4Affected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 8.8 Telecommunications Update ServiceAffected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 7 Extended Lifecycle SupportAffected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 10.0 Extended Update SupportAffected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 9.6 Extended Update SupportAffected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update SupportAffected versions are unavailable in this record.
389 Directory Server · Red Hat Trusted Artifact SignerAffected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 8Affected versions are unavailable in this record.
389 Directory Server · Logging Subsystem for Red Hat OpenShiftAffected versions are unavailable in this record.
389 Directory Server · Red Hat AI Inference ServerAffected versions are unavailable in this record.

Published CVSS scores

7.5Red HatCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
8.9GitHubCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-409Improper Handling of Highly Compressed Data (Data Amplification)
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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