# CVE-2026-27171: Denial of service in zlib

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

- **Severity:** Low 2.9 (`CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 18 Feb 2026
- **Updated:** 18 Feb 2026
- **Also known as:** ALPINE-CVE-2026-27171, AZL-77886, AZL-77981, AZL-77985, AZL-77988, AZL-77990, AZL-77993, AZL-78000, AZL-78009, AZL-78012, AZL-78014, AZL-78017, AZL-78021, AZL-78024, AZL-78027, AZL-78120, AZL-78179, AZL-78203, BELL-CVE-2026-27171, CLEANSTART-2026-ST77955, DEBIAN-CVE-2026-27171, ECHO-e10b-f259-a98b, GHSA-h858-mf2m-8jf4, JLSEC-2026-480, MGASA-2026-0076, MINI-hwjj-mj9h-qh5g, OESA-2026-1583, OESA-2026-1584, OESA-2026-1585, OESA-2026-1586, ROOT-OS-DEBIAN-11-CVE-2026-27171, ROOT-OS-DEBIAN-12-CVE-2026-27171, ROOT-OS-DEBIAN-13-CVE-2026-27171, SUSE-SU-2026:0783-1, UBUNTU-CVE-2026-27171, USN-8706-1, openSUSE-SU-2026:10617-1, openSUSE-SU-2026:12179-1

## 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 (Improper Validation of Specified Quantity in Input)

## Which versions are affected by CVE-2026-27171?

It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `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: Zlib Zlib.

## How do I fix CVE-2026-27171?

Upgrade to a fixed version.

## Is CVE-2026-27171 being exploited?

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

## Other vulnerabilities in zlib

- [CVE-2002-0059](https://insights.sbomify.com/CVE-2002-0059/): Use after free in n/a (critical 9.8)
- [CVE-2005-2096](https://insights.sbomify.com/CVE-2005-2096/): Memory corruption in n/a (high 7.5)
- [CVE-2003-0107](https://insights.sbomify.com/CVE-2003-0107/): Memory corruption in n/a (high 7.5)
- [CVE-2005-1849](https://insights.sbomify.com/CVE-2005-1849/): Denial of service in n/a (medium 5.0)
- [CVE-2026-22184](https://insights.sbomify.com/CVE-2026-22184/): zlib <= 1.3.1.2 untgz Global Buffer Overflow in TGZfname() (medium 4.6)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-27171 and fix it if it is affected.

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

Affected product: zlib. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-27171/ (Markdown: https://insights.sbomify.com/CVE-2026-27171/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-27171
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-27171
- OSV: https://osv.dev/vulnerability/CVE-2026-27171

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-27171/
Summaries are generated and may contain mistakes; the official description above is the record.