CVE-2026-45409

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Last Modified: UTC

Moderate Moderate severity What does this mean?
5.3 CVSS v3 Score Breakdown

Description

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.

Statement

A flaw was found in the python-idna library. This is an incomplete fix for CVE-2024-3651. The idna.encode() function performs contextual validation checks (valid_contexto) before rejecting oversized inputs, allowing specially crafted long payloads to cause excessive CPU consumption and lead to a denial of service. The fix in version 3.14 rejects long inputs early before further processing, and version 3.15 extends this approach to alternate per-label conversion and codec functions.

Mitigation

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 validation checks (e.g.: DNS length < 254 chars) are affected.

Additional information

External References

Affected Packages and Issued Red Hat Security Errata

Unless explicitly stated as not affected, all previous versions of packages in any minor update stream of a product listed here should be assumed vulnerable, although may not have been subject to full analysis.

Products / Services Components State Errata
Red Hat Discovery 2 discovery/discovery-ui-rhel9 Fixed RHSA-2026:61783
Red Hat Enterprise Linux 10 python-idna Fixed RHSA-2026:54481
Red Hat Enterprise Linux 8 python-idna Fixed RHSA-2026:54290
Red Hat Enterprise Linux 9 python-idna Fixed RHSA-2026:54484
Red Hat Hardened Images jaeger-main Fixed RHSA-2026:25039
Red Hat Hardened Images python-idna-main Fixed RHSA-2026:25503
Red Hat Hardened Images python-rpds-py-main Fixed RHSA-2026:34119
Red Hat Openshift Data Foundation 4.18 odf4/cephcsi-rhel9 Fixed This content is not included.RHSA-2026:56431
Red Hat Openshift Data Foundation 4.18 odf4/cephcsi-rhel9-operator Fixed This content is not included.RHSA-2026:56431
Red Hat Openshift Data Foundation 4.18 odf4/mcg-core-rhel9 Fixed This content is not included.RHSA-2026:56431

Common Vulnerability Scoring System (CVSS) Score Details

Important note

CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authorities (CNA) source for its products and services (see Red Hat classifications ).

CVSS v3 Score Breakdown

Red Hat NVD cve.org
CVSS v3 Base Score 5.3 5.3 N/A
Attack Vector Network Network N/A
Attack Complexity Low Low N/A
Privileges Required None None N/A
User Interaction None None N/A
Scope Unchanged Unchanged N/A
Confidentiality Impact None None N/A
Integrity Impact None None N/A
Availability Impact Low Low N/A

CVSS v3 Vector

Red Hat CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

NVD CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Frequently Asked Questions

Why is Red Hat's CVSS v3 score or Impact different from other vendors?

 For open source software shipped by multiple vendors, the CVSS base scores may vary for each vendor's version depending on the version they ship, how they ship it, the platform, and even how the software is compiled. This makes scoring of vulnerabilities difficult for third-party vulnerability databases such as NVD that only provide a single CVSS base score for each vulnerability. Red Hat scores reflect how a vulnerability affects our products specifically.

For more information, see https://access.redhat.com/solutions/762393.

My product is listed as "Under investigation" or "Affected", when will Red Hat release a fix for this vulnerability?
  • "Under investigation" doesn't necessarily mean that the product is affected by this vulnerability. It only means that our Analysis Team is still working on determining whether the product is affected and how it is affected.
  • "Affected" means that our Analysis Team has determined that this product is affected by this vulnerability and might release a fix to address this in the near future.

What can I do if my product is listed as "Will not fix"?

 A "will not fix" status means that a fix for an affected product version is not planned or not possible due to complexity, which may create additional risk.

Available options depend mostly on the Impact of the vulnerability and the current Life Cycle phase of your product. Overall, you have the following options:
  • Upgrade to a supported product version that includes a fix for this vulnerability (recommended).
  • Apply a mitigation (if one exists).
  • Open a This content is not included.support case to request a prioritization of releasing a fix for this vulnerability.

What can I do if my product is listed as "Fix deferred"?

 A deferred status means that a fix for an affected product version is not guaranteed due to higher-priority development work.

Available options depend mostly on the Impact of the vulnerability and the current Life Cycle phase of your product. Overall, you have the following options:
  • Apply a mitigation (if one exists).
  • Open a This content is not included.support case to request a prioritization of releasing a fix for this vulnerability.
  • Red Hat Engineering focuses on addressing high-priority issues based on their complexity or limited lifecycle support. Therefore, lower-priority issues will not receive immediate fixes.

What is a mitigation?

 A mitigation is an action that can be taken to reduce the impact of a security vulnerability, without deploying any fixes.

I have a Red Hat product but it is not in the above list, is it affected?

 The listed products were found to include one or more of the components that this vulnerability affects. These products underwent a thorough evaluation to determine their affectedness by this vulnerability. Note that layered products (such as container-based offerings) that consume affected components from any of the products listed in this table may be affected and are not represented.

Why is my security scanner reporting my product as vulnerable to this vulnerability even though my product version is fixed or not affected?

 In order to maintain code stability and compatibility, Red Hat usually does not rebase packages to entirely new versions. Instead, we backport fixes and new features to an older version of the package we distribute. This can result in some security scanners that only consider the package version to report the package as vulnerable. To avoid this, we suggest that you use an approved vulnerability scanner from our This content is not included.Red Hat Vulnerability Scanner Certification program.

My product is listed as "Out of Support Scope". What does this mean?

 When a product is listed as "Out of Support Scope", it means a vulnerability with the impact level assigned to this CVE is no longer covered by its current support lifecycle phase. The product has been identified to contain the impacted component, but analysis to determine whether it is affected or not by this vulnerability was not performed. The product should be assumed to be affected. Customers are advised to apply any mitigation options documented on this page, consider removing or disabling the impacted component, or upgrade to a supported version of the product that has an update available.