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No exploitation reportedFix available

CVE-2026-45409

No exploitation reported by the sources we read.

  • Published2026-06-05
  • Fixed in3.15
  • WeaknessCWE-1333

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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.

Timeline

dates in UTC
  1. 2026-06-0523:16CVE publishedNVD

Versions per branch

NVD · OSV
Kjd internationalized domain names in applications
BranchAffectedFixed in
3.15< 3.153.15

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Products declared by the CNA1 product

As GitHub_M, the CNA that assigned this CVE, declared them in the CVE record; versions as written.

  • kjd idna
    Affected
    • = < 3.15no fix stated

Source: the CNA record (CVE Program), © The MITRE Corporation,CVE Terms of UseCVE recordupdated 2026-06-05

Distribution builds and vendor advisories

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

  • acapy-agent-1.3MinimOSall versions · fixed in 1.3.5-r0
  • acapy-agent-1.6MinimOSall versions · fixed in 1.6.2-r0
  • airflow-2CleanStartall versions · fixed in 2.10.3-r2
  • airflow-2CleanStartall versions · fixed in 2.11.2-r1
  • airflow-2Chainguardall versions · no fixed version listedand 6 other packages
  • airflow-3Wolfiall versions · fixed in 3.2.1-r4
  • airflow-3MinimOSall versions · fixed in 3.3.0-r0
  • airflow-3CleanStartall versions · fixed in 3.2.0-r0

414 more package ranges on OSV.dev

Vendor advisories

  • CVE-2026-45409 Red Hat Product Security93 products fixed · 319 known affected

    python-idna: idna: Denial of Service via specially crafted long inputs

    confidential-clusters-beta/attestation-key-register-rhel9 as a component of Confidential Cluster Operator · confidential-clusters-beta/compute-pcrs-rhel9 as a component of Confidential Cluster Operator · confidential-clusters-beta/confidential-cluster-operator-bundle as a component of Confidential Cluster Operator · +316 more

  • RHSA-2026:66018 Red Hat Product Security5 products fixed

    Red Hat Security Advisory: Red Hat Update Infrastructure 5.3 security update

  • RHSA-2026:61783 Red Hat Product Security2 products fixed

    Red Hat Security Advisory: A Subscription Management tool for finding and reporting Red Hat product usage

  • RHSA-2026:58981 Red Hat Product Security3 products fixed

    Red Hat Security Advisory: Red Hat Update Infrastructure 5.3 Technology Preview security update

  • RHSA-2026:56431 Red Hat Product Security68 products fixed

    Red Hat Security Advisory: Red Hat OpenShift Data Foundation 4.18.27 security, enhancement & bug fix update

  • RHSA-2026:54484 Red Hat Product Security2 products fixed

    Red Hat Security Advisory: python-idna security update

5 more advisories

Full record on NVD

Fix

  1. Update Kjd internationalized domain names in applications to 3.15
  2. Vendor fix Red Hat Product Security RHSA-2026:66018 · 5 productsThe container images provided by this release, apart from the installer, should be deployed using rhui-installer utility. See the official documentation for more details.
  3. Vendor fix Red Hat Product Security RHSA-2026:61783 · 2 productsThe containers required to run Discovery can be installed through discovery-installer RPM. See the official documentation for more details.
  4. Vendor fix Red Hat Product Security RHSA-2026:58981 · 3 productsPlease consult the RHUI Technology Preview Release Notes at https://access.redhat.com/articles/7141172 for instructions on how to use this image set.
  5. Vendor fix Red Hat Product Security RHSA-2026:56431 · 68 productsBefore applying this update, make sure all previously released errata relevant to your system have been applied. For details on how to apply this update, refer to: https://docs.redhat.com/en/documentation/red_hat_openshift_data_foundation/4.18/html/updating_openshift_data_foundation/updating-ocs-…
  6. Vendor fix Red Hat Product Security RHSA-2026:54484 · 2 productsFor details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258
  7. Vendor fix Red Hat Product Security RHSA-2026:34119 · 3 productsFor details on how to apply this update, which includes the changes described in this advisory, refer to: https://images.redhat.com/

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof of concept
Metasploit modules
none listed
Metasploit Framework

Sources

  • CISA-ADPSSVC decisionnone2026-06-08
  • CNACVSS 4.06.9known since 2026-10-23
  • NVDCVSS 3.15.3read 2026-10-23
  • CNAweakness (CWE)CWE-1333known since 2026-10-23
  • FIRST EPSSEPSS score0.4 %2026-11-08
  • OSVaffected packages—
  • GitHub AdvisoriesadvisoryMODERATE2026-05-19

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
CVSS 4.0 vector
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Published
2026-06-05
Last Modified
2026-07-23
NVD status
Analyzed
GitHub Advisory
GHSA-65pc-fj4g-8rjx

Frequently asked questions

What is CVE-2026-45409?

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.

Is CVE-2026-45409 actively exploited?

Active exploitation of CVE-2026-45409 has not been confirmed. Its EPSS score was 0.4% on 2026-11-08, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-45409?

CVE-2026-45409 has a CVSS v3 base score of 5.3 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.

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