Ubuntu published security notice USN-8515-1 to address a denial of service flaw discovered in the ruby-addressable package. The bug stems from incorrect handling of specific URI templates, which generates regular expressions prone to catastrophic backtracking when processing malicious input. Systems running Ubuntu versions from 16.04 LTS through 26.04 LTS all require immediate package updates to prevent resource exhaustion attacks.

[USN-8515-1] Addressable vulnerability

[USN-8515-1] Addressable vulnerability

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Ubuntu Security Notice USN-8515-1
July 07, 2026

ruby-addressable vulnerability
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 26.04 LTS
- Ubuntu 24.04 LTS
- Ubuntu 22.04 LTS
- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS

Summary:

Addressable could be made to consume resources and cause a denial of
service if it received specially crafted input.

Software Description:
- ruby-addressable: Addressable is an alternative implementation to the URI implementation that is part of Ruby's standard library

Details:

It was discovered that Addressable incorrectly handled certain URI
templates, generating regular expressions vulnerable to catastrophic
backtracking. An attacker could use this issue to craft a URI that, when matched
against a vulnerable template, causes excessive resource consumption,
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
ruby-addressable 2.8.7-2ubuntu0.26.04.1~esm1
Available with Ubuntu Pro

Ubuntu 24.04 LTS
ruby-addressable 2.8.5-1ubuntu0.1~esm1
Available with Ubuntu Pro

Ubuntu 22.04 LTS
ruby-addressable 2.8.0-3ubuntu0.1~esm1
Available with Ubuntu Pro

Ubuntu 20.04 LTS
ruby-addressable 2.7.0-1ubuntu0.1~esm1
Available with Ubuntu Pro

Ubuntu 18.04 LTS
ruby-addressable 2.5.2-1ubuntu0.1~esm1
Available with Ubuntu Pro

Ubuntu 16.04 LTS
ruby-addressable 2.3.8-1ubuntu0.1~esm1
Available with Ubuntu Pro

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

References:
https://ubuntu.com/security/notices/USN-8515-1
CVE-2026-35611