zlib up to 1.3.1 crc32_combine64/crc32_combine_gen64 improper validation of specified quantity in input

CVSS Meta Temp Score
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CTI Interest Score
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4.2$0-$5k0.00

Summaryinfo

A vulnerability classified as problematic has been found in zlib up to 1.3.1. The affected element is the function crc32_combine64/crc32_combine_gen64. This manipulation causes improper validation of specified quantity in input. The identification of this vulnerability is CVE-2026-27171. It is possible to initiate the attack remotely. There is no exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic was found in zlib up to 1.3.1. Affected by this vulnerability is the function crc32_combine64/crc32_combine_gen64. The manipulation with an unknown input leads to a improper validation of specified quantity in input vulnerability. The CWE definition for the vulnerability is CWE-1284. The product receives input that is expected to specify a quantity (such as size or length), but it does not validate or incorrectly validates that the quantity has the required properties. As an impact it is known to affect availability. The summary by CVE is:

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.

The advisory is shared at github.com. This vulnerability is known as CVE-2026-27171 since 02/18/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. It demands that the victim is doing some kind of user interaction. Technical details are known, but no exploit is available.

The vulnerability scanner Nessus provides a plugin with the ID 299392 (Linux Distros Unpatched Vulnerability : CVE-2026-27171), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 1.3.2 eliminates this vulnerability. The upgrade is hosted for download at github.com.

The vulnerability is also documented in the databases at Tenable (299392) and CERT Bund (WID-SEC-2026-0435). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Affected

  • Open Source zlib

Productinfo

Name

Version

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 4.2
VulDB Meta Temp Score: 4.2

VulDB Base Score: 4.3
VulDB Temp Score: 4.1
VulDB Vector: 🔒
VulDB Reliability: 🔍

NVD Base Score: 5.5
NVD Vector: 🔒

CNA Base Score: 2.9
CNA Vector (MITRE): 🔒

CVSSv2info

AVACAuCIA
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Improper validation of specified quantity in input
CWE: CWE-1284 / CWE-703
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 299392
Nessus Name: Linux Distros Unpatched Vulnerability : CVE-2026-27171

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: zlib 1.3.2

Timelineinfo

02/18/2026 Advisory disclosed
02/18/2026 +0 days CVE reserved
02/18/2026 +0 days VulDB entry created
02/21/2026 +3 days VulDB entry last update

Sourcesinfo

Advisory: 904
Status: Confirmed

CVE: CVE-2026-27171 (🔒)
GCVE (CVE): GCVE-0-2026-27171
GCVE (VulDB): GCVE-100-346429
CERT Bund: WID-SEC-2026-0435 - zlib: Schwachstelle ermöglicht Denial of Service

Entryinfo

Created: 02/18/2026 06:58
Updated: 02/21/2026 17:40
Changes: 02/18/2026 06:58 (64), 02/18/2026 17:30 (7), 02/18/2026 19:49 (2), 02/21/2026 17:40 (12)
Complete: 🔍
Cache ID: 216::103

If you want to get the best quality for vulnerability data then you always have to consider VulDB.

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