--- id: CVE-2026-45409 title: >- python-idna: idna: Denial of Service via specially crafted long inputs (CVE-2026-45409) summary: >- A flaw was found in the idna library, which handles Internationalized Domain Names in Python applications. A remote attacker could exploit this vulnerability by sending specially crafted, excessively long inputs to the library's encoding f… severity: medium cvss: 5.3 cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L' cvssSource: vendor cwe: CWE-770 vendor: Red Hat product: Red Hat Enterprise Linux 9 affected: - confidential_cluster_operator - exploit_intelligence - external_secrets_operator_for_red_hat_openshift - migration_toolkit_for_applications 8 - migration_toolkit_for_containers - migration_toolkit_for_virtualization - openshift_lightspeed - openshift_service_mesh 3 - advanced_cluster_management_for_kubernetes 2 - ai_inference_server - ansible_automation_platform 2 - ansible_automation_platform_ansible_core 2 - build_of_quarkus_native_builder - developer_hub - enterprise_linux 10 - enterprise_linux 7 - enterprise_linux 8 - enterprise_linux 9 - enterprise_linux_ai_rhel_ai 3 - openshift_ai_rhoai - openshift_container_platform 4 - openshift_virtualization 4 - satellite 6 - trusted_artifact_signer - update_infrastructure_4_for_cloud_providers - self_service_automation_portal 2 - service_telemetry_framework 1.5 - enterprise_linux_baseos_v_10 - enterprise_linux_baseos_v_8 - enterprise_linux_baseos_v_9 - discovery 2 - hardened_images - openshift_data_foundation 4.18 - update_infrastructure 5 patched: - enterprise_linux_baseos_v_10 - enterprise_linux_baseos_v_8 - enterprise_linux_baseos_v_9 - discovery 2 - hardened_images - openshift_data_foundation 4.18 - update_infrastructure 5 published: '2026-06-05' updated: '2026-09-10' sourceUpdated: '2026-09-10T17:23:38+00:00' source: CSAF sourceUrl: 'https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-45409.json' references: - url: >- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-45409.json - url: 'https://access.redhat.com/security/cve/CVE-2026-45409' - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2485616' - url: 'https://www.cve.org/CVERecord?id=CVE-2026-45409' - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-45409' - url: 'https://github.com/kjd/idna/security/advisories/GHSA-65pc-fj4g-8rjx' - url: 'https://access.redhat.com/errata/RHSA-2026:54481' - url: 'https://access.redhat.com/errata/RHSA-2026:54290' - url: 'https://access.redhat.com/errata/RHSA-2026:54484' - url: 'https://access.redhat.com/errata/RHSA-2026:61783' - url: 'https://access.redhat.com/errata/RHSA-2026:25039' - url: 'https://access.redhat.com/errata/RHSA-2026:25503' - url: 'https://access.redhat.com/errata/RHSA-2026:34119' - url: 'https://access.redhat.com/errata/RHSA-2026:56431' - url: 'https://access.redhat.com/errata/RHSA-2026:66018' - url: 'https://access.redhat.com/errata/RHSA-2026:58981' - url: 'https://github.com/kjd/idna' - url: >- https://github.com/pypa/advisory-database/tree/main/vulns/idna/PYSEC-2026-215.yaml tags: - csaf - vex - red-hat - osv - pip epss: 0.00408 epssPercentile: 0.34826 aliases: - GHSA-65pc-fj4g-8rjx - PYSEC-2026-215 ecosystem: pip ingestedAt: '2026-07-08T18:25:46.288Z' --- ## Overview A flaw was found in the idna library, which handles Internationalized Domain Names in Python applications. A remote attacker could exploit this vulnerability by sending specially crafted, excessively long inputs to the library's encoding function. This could cause the system to consume significant resources, leading to a Denial of Service (DoS), where the affected application becomes unavailable to legitimate users. This issue stems from an incomplete fix for a previously identified vulnerability. ## Vendor advisories - **RHSA-2026:54481** · Red Hat · fixed in: Red Hat Enterprise Linux BaseOS (v. 10) · released 2026-08-13 · [advisory](https://access.redhat.com/errata/RHSA-2026:54481) - **RHSA-2026:54290** · Red Hat · fixed in: Red Hat Enterprise Linux BaseOS (v. 8) · released 2026-08-12 · [advisory](https://access.redhat.com/errata/RHSA-2026:54290) - **RHSA-2026:54484** · Red Hat · fixed in: Red Hat Enterprise Linux BaseOS (v. 9) · released 2026-08-13 · [advisory](https://access.redhat.com/errata/RHSA-2026:54484) - **RHSA-2026:61783** · Red Hat · fixed in: Red Hat Discovery 2 · released 2026-08-31 · [advisory](https://access.redhat.com/errata/RHSA-2026:61783) - **RHSA-2026:25039** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-06-10 · [advisory](https://access.redhat.com/errata/RHSA-2026:25039) - **RHSA-2026:25503** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-06-12 · [advisory](https://access.redhat.com/errata/RHSA-2026:25503) - **RHSA-2026:34119** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-07-01 · [advisory](https://access.redhat.com/errata/RHSA-2026:34119) - **RHSA-2026:56431** · Red Hat · fixed in: Red Hat Openshift Data Foundation 4.18 · released 2026-08-18 · [advisory](https://access.redhat.com/errata/RHSA-2026:56431) - **RHSA-2026:66018** · Red Hat · fixed in: Red Hat Update Infrastructure 5 · released 2026-09-09 · [advisory](https://access.redhat.com/errata/RHSA-2026:66018) - **RHSA-2026:58981** · Red Hat · fixed in: Red Hat Update Infrastructure 5 · released 2026-08-24 · [advisory](https://access.redhat.com/errata/RHSA-2026:58981) - **Red Hat VEX** · Moderate · affected: Confidential Cluster Operator, Exploit Intelligence, External Secrets Operator for Red Hat OpenShift, Migration Toolkit for Applications 8, Migration Toolkit for Containers, Migration Toolkit for Virtualization, … · no fix planned: Confidential Cluster Operator, Exploit Intelligence, External Secrets Operator for Red Hat OpenShift, Migration Toolkit for Applications 8, … · updated 2026-09-10 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-45409.json) **python-idna: idna: Denial of Service via specially crafted long inputs** — rated Moderate by Red Hat. Released 2026-06-05, updated 2026-09-10. Affected: - Confidential Cluster Operator - Exploit Intelligence - External Secrets Operator for Red Hat OpenShift - Migration Toolkit for Applications 8 - Migration Toolkit for Containers - Migration Toolkit for Virtualization - OpenShift Lightspeed - OpenShift Service Mesh 3 - Red Hat Advanced Cluster Management for Kubernetes 2 - Red Hat AI Inference Server - Red Hat Ansible Automation Platform 2 - Red Hat Ansible Automation Platform Ansible Core 2 - Red Hat build of Quarkus Native builder - Red Hat Developer Hub - Red Hat Enterprise Linux 10 - Red Hat Enterprise Linux 7 - Red Hat Enterprise Linux 8 - Red Hat Enterprise Linux 9 - Red Hat Enterprise Linux AI (RHEL AI) 3 - Red Hat OpenShift AI (RHOAI) - Red Hat OpenShift Container Platform 4 - Red Hat OpenShift Virtualization 4 - Red Hat Satellite 6 - Red Hat Trusted Artifact Signer - Red Hat Update Infrastructure 4 for Cloud Providers - Self-service automation portal 2 - Service Telemetry Framework 1.5 Fixed: - Red Hat Enterprise Linux BaseOS (v. 10) - Red Hat Enterprise Linux BaseOS (v. 8) - Red Hat Enterprise Linux BaseOS (v. 9) - Red Hat Discovery 2 - Red Hat Hardened Images - Red Hat Openshift Data Foundation 4.18 - Red Hat Update Infrastructure 5 No fix planned: - Confidential Cluster Operator - Exploit Intelligence - External Secrets Operator for Red Hat OpenShift - Migration Toolkit for Applications 8 - Migration Toolkit for Containers - Migration Toolkit for Virtualization - OpenShift Lightspeed - OpenShift Service Mesh 3 - Red Hat Advanced Cluster Management for Kubernetes 2 - Red Hat AI Inference Server - Red Hat Ansible Automation Platform 2 - Red Hat Ansible Automation Platform Ansible Core 2 - Red Hat build of Quarkus Native builder - Red Hat Developer Hub - Red Hat Enterprise Linux 10 - Red Hat Enterprise Linux 7 - Red Hat Enterprise Linux 8 - Red Hat Enterprise Linux 9 - Red Hat Enterprise Linux AI (RHEL AI) 3 - Red Hat OpenShift AI (RHOAI) - Red Hat OpenShift Container Platform 4 - Red Hat OpenShift Virtualization 4 - Red Hat Satellite 6 - Red Hat Trusted Artifact Signer - Red Hat Update Infrastructure 4 for Cloud Providers - Self-service automation portal 2 - Service Telemetry Framework 1.5 Not affected: - Red Hat Discovery 2 - Red Hat Openshift Data Foundation 4.18 - Red Hat Update Infrastructure 5 - Confidential Cluster Operator - Confidential Compute Attestation - Lightspeed Core - Logging Subsystem for Red Hat OpenShift - OpenShift Lightspeed - OpenShift Service Mesh 3 - Pen Drive Powered by Red Hat Lightspeed ## Remediation For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258 https://access.redhat.com/errata/RHSA-2026:54481 For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258 https://access.redhat.com/errata/RHSA-2026:54290 For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258 https://access.redhat.com/errata/RHSA-2026:54484 Workarounds / mitigations: - To mitigate this denial-of-service vulnerability, applications utilizing the `idna` Python library should implement input validation to ensure that domain names do not exceed the standard 253-character length limit before being passed to the `idna.encode()` function. This operational control prevents the processing of excessively long inputs that could lead to resource exhaustion and service unavailability. Applications that pass user-controlled data directly to `idna.encode()` without validat… ## Package advisory (CVE-2026-45409) Affected packages: - `idna < 3.15` Patched in: - `idna 3.15` Source: https://osv.dev/vulnerability/GHSA-65pc-fj4g-8rjx