CVE-2026-27171 Denial of service in zlib

Low 2.9 Published 18 Feb 2026 Updated 18 Feb 2026

An attacker can cause CPU exhaustion in applications using zlib via specific CRC functions due to a missing loop termination condition.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Local or same network only
Victim action needed: Not needed
Fix: Available

What is CVE-2026-27171?

CVE-2026-27171 is a low-severity denial of service vulnerability in zlib, published on 18 Feb 2026. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

zlib before 1.3.2 allows CPU consumption via crc32_combine64 and crc32_combine_gen64 because x2nmodp can do right shifts within a loop that has no termination condition.

Weakness: CWE-1284

Which versions are affected by CVE-2026-27171?

It affects 1 product.

Linux distribution packages (6)

`zlib` SUSE:Linux Enterprise Micro 5.5	All versions	`1.2.13-150500.4.6.1`
`zlib` SUSE:Linux Enterprise Module for Basesystem 15 SP7	All versions	`1.2.13-150500.4.6.1`
`zlib` SUSE:Linux Enterprise Module for Development Tools 15 SP7	All versions	`1.2.13-150500.4.6.1`
`zlib` openSUSE:Leap 15.6	All versions	`1.2.13-150500.4.6.1`
`freetype2` openSUSE:Tumbleweed	All versions	`2.15.0-1.1`
`zlib` openSUSE:Tumbleweed	All versions	`1.3.1-2.1`

Products include Zlib Zlib.

How do I fix CVE-2026-27171?

Upgrade to a fixed version.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2026-27171 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-27171 exists.

Sources

Also known as ALPINE-CVE-2026-27171, AZL-77886, AZL-77981, AZL-77985, AZL-77988, AZL-77990 and 32 more.