USN-8219-1: UltraJSON vulnerabilities

Publication date

28 April 2026

Overview

Several security issues were fixed in UltraJSON.


Packages

  • ujson - Ultra fast JSON encoder and decoder

Details

Cameron Criswell discovered that UltraJSON contained a memory leak
that would occur when parsing large integers. An attacker could
possibly use this issue to cause UltraJSON to crash, resulting in a
denial of service. This issue only affected Ubuntu 24.04 LTS,
Ubuntu 25.10, and Ubuntu 26.04 LTS. (CVE-2026-32874)

It was discovered that UltraJSON contained integer overflow/underflow
issues when calculating how much memory to reserve for indentation in
certain instances. An attacker could possibly use this issue to cause
UltraJSON to crash, resulting in a denial of service. (CVE-2026-32875)

Cameron Criswell discovered that UltraJSON contained a memory leak
that would occur when parsing large integers. An attacker could
possibly use this issue to cause UltraJSON to crash, resulting in a
denial of service. This issue only affected Ubuntu 24.04 LTS,
Ubuntu 25.10, and Ubuntu 26.04 LTS. (CVE-2026-32874)

It was discovered that UltraJSON contained integer overflow/underflow
issues when calculating how much memory to reserve for indentation in
certain instances. An attacker could possibly use this issue to cause
UltraJSON to crash, resulting in a denial of service. (CVE-2026-32875)

Update instructions

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

Learn more about how to get the fixes.

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

Ubuntu Release Package Version
26.04 LTS resolute python3-ujson –  5.11.0-3ubuntu0.1
25.10 questing python3-ujson –  5.10.0-1ubuntu0.1
24.04 LTS noble python3-ujson –  5.9.0-1ubuntu0.1~esm1  
22.04 LTS jammy python3-ujson –  5.1.0-1ubuntu0.1~esm2  

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