CVE-2026-45409
📛 CVE Title
(no title)
Description
Internationalized Domain Names in Applications (IDNA): Specially crafted inputs to idna.encode() can bypass CVE-2024-3651 fix
Description (MITRE) cveawg.mitre.org
Pulled from cveawg.mitre.org/api/cve/CVE-2026-45409 on 2026-07-31. Shown when MITRE's text differs from the cvelistV5 mirror.
Internationalized Domain Names in Applications (IDNA) for Python provides support for Internationalized Domain Names in Applications (IDNA) and Unicode IDNA Compatibility Processing. In versions prior to 3.15, payloads such as `"\u0660" * N` or `"\u30fb" * N + "\u6f22"` utilize the `valid_contexto` function prior to length rejection, and for high values of `N` will take a long time to process. This is the same issue as CVE-2024-3651, however the original remediation in 2024 was not a complete fix. A specially crafted argument to the `idna.encode()` function could consume significant resources. This may lead to a denial-of-service. Starting in version 3.14, the function rejects long inputs as soon as practicable prior to any further processing to minimize resource consumption. In version 3.15, this approach was extended to lesser used alternate functions (i.e. per-label conversions and codec support). A workaround is available. Domain names cannot exceed 253 characters in length. If this length limit is enforced prior to passing the domain to the `idna.encode()` function, it should no longer consume significant resources. This is triggered by arbitrarily large inputs that would not occur in normal usage, but may be passed to the library assuming there is no preliminary input validation by the higher-level application.
Overview
- State
- —
- Assigner (CNA)
- —
- CVSS severity
- critical
- CVSS score
- 9.1 / 10
- CVSS vector
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H- Effective score
- 9.1 / 10 CRITICAL source: CNA overview
- CWE(s)
- —
- Reserved
- —
- Published
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- Last updated
- —
- Source
- https://www.tenable.com/cve/CVE-2026-45409
- Linked Threat
- CVE-2026-45409 — CVE-2026-45409
NVD / KEV / EPSS data refreshed 2026-05-25 00:13 UTC. Re-run the 🛰 Backfill from NVD button above to refresh.
European Union Vulnerability Database ENISA EUVD
ENISA's official EU repository for curated vulnerability intelligence. Carries a separate identifier (EUVD-YYYY-NNNN) and frequently exposes an earlier-published description + CVSS than NVD does.
- EUVD ID
-
EUVD-2026-34921 - Assigner
- GitHub_M
- Published
- Jun 5, 2026, 10:06:07 PM
- Updated
- Jun 8, 2026, 4:34:00 PM
- EUVD base score (CVSS 4.0)
-
6.9 / 10
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N - EUVD-reported EPSS
- 0.4100
- Vendors
- kjd
- Products
-
idna (< 3.15)
- Aliases
-
GHSA-65pc-fj4g-8rjx
ENISA description: Internationalized Domain Names in Applications (IDNA) for Python provides support for Internationalized Domain Names in Applications (IDNA) and Unicode IDNA Compatibility Processing. In versions prior to 3.15, payloads such as `"\u0660" * N` or `"\u30fb" * N + "\u6f22"` utilize the `valid_contexto` function prior to length rejection, and for high values of `N` will take a long time to process. This is the same issue as CVE-2024-3651, however the original remediation in 2024 was not a complete fix. A specially crafted argument to the `idna.encode()` function could consume significant resources. This may lead to a denial-of-service. Starting in version 3.14, the function rejects long inputs as soon as practicable prior to any further processing to minimize resource consumption. In version 3.15, this approach was extended to lesser used alternate functions (i.e. per-label conversions and codec support). A workaround is available. Domain names cannot exceed 253 characters in length. If this length limit is enforced prior to passing the domain to the `idna.encode()` function, it should no longer consume significant resources. This is triggered by arbitrarily large inputs that would not occur in normal usage, but may be passed to the library assuming there is no preliminary input validation by the higher-level application.
EUVD references (1)
Vendor references (0)
References embedded in the original CVE record by the assigning CNA.
None in the CVE record.
MITRE references (1) cveawg.mitre.org
Pulled from MITRE's CVE Services API by the 🛰 Backfill from MITRE button.
- https://github.com/kjd/idna/security/advisories/GHSA-65pc-fj4g-8rjx x_refsource_CONFIRM
Web references (2)
DuckDuckGo results ranked by threat-intel / vendor advisory domains. Generated by the 🔎 Find references (web) button above — same flow as the Remediations search.
- https://nvd.nist.gov/vuln/detail/CVE-2026-45409 tenable:nvd.nist.gov
- https://www.cve.org/CVERecord?id=CVE-2026-45409 tenable:www.cve.org
Remediations (10)
Remediations are stored against the linked Threat row; the list below is deduplicated across both pages.
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web:blog.qualys.com
With Qualys Policy Audit's out-of-the-box mitigation or Compensatory Controls, which reduce the risk of a vulnerability being exploited because the remediation ( fix / patch ) cannot be done immediately, these security controls are not recommended by any industry standards, such as CIS and DISA-STIG.
2026-05-26 02:58 UTC -
web:community.ui.com
Published: May 21, 2026 Updated: May 22, 2026 Version: 1.1 Revision: 1.1 Summary 1 of 5 A malicious actor with access to the network and high privileges could exploit an Improper Input Validation vulnerability found in UniFi OS devices to execute a Command Injection. Affected Products: UniFi OS Server (Version 5.0.6 and earlier) Mitigation : Update your UniFi OS Server to Version 5.0.8 or later ...
2026-05-26 02:58 UTC -
web:cyberpress.org
The U.S. Cybersecurity and Infrastructure Security Agency (CISA) has added two actively exploited Microsoft Defender vulnerabilities to its Known Exploited Vulnerabilities (KEV) catalog, issuing an urgent remediation directive for federal agencies with a due date of June 3, 2026 .
2026-05-26 02:58 UTC -
web:cybersecuritynews.com
The U.S. Cybersecurity and Infrastructure Security Agency (CISA) has added two critical Microsoft Defender vulnerabilities to its Known Exploited Vulnerabilities (KEV) catalog, warning organizations of active exploitation risks. The flaws, tracked as CVE - 2026 -45498 and CVE - 2026 -41091, impact Microsoft Defender and could allow attackers to disrupt systems or escalate privileges. Both ...
2026-05-26 02:58 UTC -
web:msrc.microsoft.com
The Microsoft Security Response Center (MSRC) investigates all reports of security vulnerabilities affecting Microsoft products and services, and provides the information here as part of the ongoing effort to help you manage security risks and help keep your systems protected.
2026-05-26 02:58 UTC -
web:op-c.net
CISA has added two Microsoft Defender vulnerabilities to its Known Exploited Vulnerabilities catalog following evidence of active exploitation. The vulnerabilities, tracked as CVE - 2026 -41091 and CVE - 2026 -45498, affect core Microsoft Defender components used to protect Windows endpoints. CISA added both vulnerabilities to KEV on May 20, 2026 , with a federal remediation due date of June 3, 2026 .
2026-05-26 02:58 UTC -
web:support.servicenow.com
Overview The advisories below document publicly disclosed Common Vulnerabilities and Exposures ( CVEs ) in the Now Platform by ServiceNow. Because ServiceNow uses various methods to communicate vulnerability information, patches, and other fixes, customers should review family, security patch , and hotfix release notes, which are available at https://docs.servicenow.com, for a complete list of ...
2026-05-26 02:58 UTC -
web:www.helpnetsecurity.com
Attackers are actively exploiting two Microsoft Defender vulnerabilities ( CVE - 2026 -41091 and CVE - 2026 -45498), Microsoft acknowledged.
2026-05-26 02:58 UTC -
web:www.oracle.com
This Critical Patch Update contains 481 new security patches across the product families listed below. Please note that an MOS note summarizing the content of this Critical Patch Update and other Oracle Software Security Assurance activities is located at April 2026 Critical Patch Update: Executive Summary and Analysis.
2026-05-26 02:58 UTC -
web:zecurit.com
Get the complete breakdown of Microsoft's May 2026 Patch Tuesday. We analyze the latest security updates and all critical CVEs .
2026-05-26 02:58 UTC
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