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[USN-8549-1] idna vulnerability

Posted on 15 July 2026
Ubuntu Security

==========================================================================Ubuntu Security Notice USN-8549-1
July 15, 2026

python-idna vulnerability
==========================================================================
A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 26.04 LTS
- Ubuntu 24.04 LTS
- Ubuntu 22.04 LTS

Summary:

idna could be made to consume resources if it received specially crafted
input.

Software Description:
- python-idna: Python IDNA2008 (RFC 5891) handling

Details:

It was discovered that idna did not properly reject oversized inputs before
performing expensive processing. An attacker could possibly use this issue
to cause idna to consume significant resources, leading to a denial of
service.

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 26.04 LTS
python3-idna 3.11-1ubuntu0.1

Ubuntu 24.04 LTS
python3-idna 3.6-2ubuntu0.2

Ubuntu 22.04 LTS
python3-idna 3.3-1ubuntu0.2

In general, a standard system update will make all the necessary changes.

References:
https://ubuntu.com/security/notices/USN-8549-1
CVE-2026-45409

Package Information:
https://launchpad.net/ubuntu/+source/python-idna/3.11-1ubuntu0.1
https://launchpad.net/ubuntu/+source/python-idna/3.6-2ubuntu0.2
https://launchpad.net/ubuntu/+source/python-idna/3.3-1ubuntu0.2

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