# zlib vulnerability affects Ubuntu 24.04, 26.04 LTS, and 26.10

> **Key takeaway:** A heap buffer overflow vulnerability in zlib could allow for denial of service or arbitrary code execution.

**Published:** 2026-10-22T19:54:53+00:00 
**Source:** Ubuntu Security & Release Notices 
**Category:** distro-news 
**Canonical URL:** https://fosswire.org/news/zlib-vulnerability-affects-ubuntu-2404-2604-lts-and-2610.html 

## Summary
Ubuntu has released security updates for the zlib lossless data-compression library to address a vulnerability discovered by Ali Firas. The issue stems from incorrect handling of certain non-blocking write operations, which could lead to a heap buffer overflow. Affected Ubuntu releases include 24.04 LTS, 26.04 LTS, and 26.10.

## Technical details of the zlib flaw
- The vulnerability is identified as **CVE-2026-85091**.
- It involves incorrect handling of **non-blocking write operations**.
- Exploitation can trigger a **heap buffer overflow**.
- Potential impacts include **denial of service (DoS)** or **arbitrary code execution**.

## Why it matters
As a fundamental data-compression library, zlib is used by a vast number of applications and system components, making this a critical update for system stability and security.