CVE-2026-45409: Internationalized Domain Names in Applications (IDNA) for Python provides support for Internationalized Domain

Routine

MEDIUM 5.3REMOTEUPGRADE

CVE-2026-45409 is a medium-severity flaw (CVSS 5.3) affecting internationalized domain names in applications. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.4% (top 65%)
CISA exploited list	No
Weakness	CWE-1333
Published	2026-06-05
Last modified	2026-07-23

Publisher (CNA): GitHub, Inc. · Vendor: kjd

Last updated 2026-07-23 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-06-05 23:16 UTCPublished CVE record published
2026-07-23 07:10 UTCUpdated Record last modified

kjd internationalized domain names in applications UPGRADE

Affected: < 3.15

Fixed in: 3.15

Safe to downgrade to: no unaffected older release

1. Check installed version

pip show internationalized-domain-names-in-applications

2. UPGRADE to 3.15

pip install --upgrade "internationalized-domain-names-in-applications>=3.15"

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-45409?

internationalized domain names in applications: upgrade to 3.15. Exact commands for each OS are on this page.

Is CVE-2026-45409 being exploited?

CVE-2026-45409 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-45409 affect?

CVE-2026-45409 affects internationalized domain names in applications. Severity is medium (CVSS 5.3). 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

How urgent is CVE-2026-45409?

Priority 32/100. Remotely exploitable, no login, no user action

Software pages

Python vulnerabilities

References

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