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Fencer Vulns
low 2.9

CVE-2026-27171 json

zlib before 1.3.2 allows CPU consumption via `crc32_combine64` and `crc32_combine_gen64` because...

published 2026-02-18 8 mo ago modified 2026-07-25 3 mo ago also EUVD-2026-8063 , GHSA-h858-mf2m-8jf4 , JLSEC-2026-480

cvss
2.9
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 16%
public exploits
0
none known

Summary

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.

Patch / fix

  • julia Openresty_jll 1.29.203+0
  • julia Zlib_jll 1.3.2+0
  • julia fmusim_jll 0.0.39001+0
  • zlib zlib 1.3.2
  • zlib Debian 13 1:1.3.dfsg+really1.3.1-1+deb13u1
  • zlib Debian 14 1:1.3.dfsg+really1.3.2-1

debian advisories DEBIAN-CVE-2026-27171

  • zlib Ubuntu 24.04 LTS 1:1.3.dfsg-3.1ubuntu2.2
  • zlib Ubuntu 26.04 LTS 1:1.3.dfsg+really1.3.1-1ubuntu3.1

ubuntu advisories UBUNTU-CVE-2026-27171

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • zlib SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 1.2.13-160000.3.1
  • zlib Linux Micro 6.1 1.2.13-slfo.1.1_2.1
  • zlib Linux Micro 6.0 1.2.13-7.1
  • zlib SLE Module for Development Tools 15 SP7, SLE Module for Basesystem 15 SP7, SLE Micro 5.5 +1 more 1.2.13-150500.4.6.1

suse advisories SUSE-SU-2026:21013-1SUSE-SU-2026:21151-1SUSE-SU-2026:20659-1SUSE-SU-2026:20709-1SUSE-SU-2026:0783-1

  • freetype2 openSUSE Tumbleweed 2.15.0-1.1
  • zlib openSUSE Tumbleweed 1.3.1-2.1
  • zlib openSUSE Leap 16.0 1.2.13-160000.3.1

opensuse advisories openSUSE-SU-2026:12179-1openSUSE-SU-2026:10617-1openSUSE-SU-2026:20487-1

  • zlib Alpine 3.24, Alpine 3.23, Alpine 3.22 +2 more 1.3.2-r0

alpine advisories ALPINE-CVE-2026-27171

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • zlib Azure Linux 3.0 1.3.2-1
  • kata-containers Azure Linux 3.0 3.19.1.kata3-6

azure linux advisories AZL-77886AZL-78120

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-27171 updated cvss 3.3

zlib: zlib: Denial of Service via infinite loop in CRC32 combine functions

  • Red Hat Logging Subsystem for Red Hat OpenShift openshift-logging/kibana6-rhel8, openshift-logging/elasticsearch6-rhel9, openshift-logging/logging-curator5-rhel9, openshift-logging/elasticsearch-proxy-rhel9, openshift-logging/elasticsearch-rhel9-operator, openshift-logging/elasticsearch-operator-bundle
    affected: no fix planned “Out of support scope”
  • Red Hat build of OpenJDK 1.8 java-1.8.0-openjdk-portable
    affected: no fix available “Fix deferred”
  • Red Hat build of OpenJDK 11 ELS java-11-openjdk, java-11-openjdk-portable
    affected: no fix planned “Out of support scope”
  • Red Hat build of OpenJDK 17 java-17-openjdk-portable Red Hat build of OpenJDK 21 java-21-openjdk-portable Red Hat build of OpenJDK 25 java-25-openjdk-portable
    affected: no fix available “Fix deferred”
  • Red Hat Enterprise Linux 6 zlib, minizip
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 7 zlib, minizip Red Hat Enterprise Linux 8 npm, zlib, mecab, mysql, rsync, nodejs, +80 more Red Hat Enterprise Linux 9 npm, zlib, mysql, rsync, nodejs, mingw-zlib, +96 more Red Hat Enterprise Linux 10 rsync, mingw-zlib, mingw32-zlib, mingw64-zlib, java-21-openjdk, java-25-openjdk Red Hat JBoss Core Services zlib Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-8, openshift/ose-rhel-coreos-9
    affected: no fix available “Fix deferred”
  • Red Hat OpenShift AI (RHOAI) rhoai/odh-core-bff-rhel9, rhoai/odh-dashboard-rhel9, rhoai/odh-mod-arch-maas-rhel9, rhoai/odh-mod-arch-automl-rhel9, rhoai/odh-mod-arch-gen-ai-rhel9, rhoai/odh-mod-arch-mlflow-rhel9, +6 more
    under investigation
  • Red Hat Enterprise Linux 8 thunderbird Red Hat Enterprise Linux 9 thunderbird Red Hat Enterprise Linux 10 thunderbird Red Hat OpenShift AI (RHOAI) rhoai/odh-mlflow-rhel9, rhoai/odh-kube-rbac-proxy-rhel9, rhoai/odh-maas-controller-rhel9, rhoai/odh-mlflow-operator-rhel9, rhoai/odh-model-controller-rhel9, rhoai/odh-ogx-k8s-operator-rhel9, +14 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
8 mo ago

Exploit prediction

0.25% chance of exploitation in the next 30 days, higher than 16% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • 7asecurity.com https://7asecurity.com/reports/pentest-report-zlib-RC1.1.pdf referenced PoC, tagged "exploit" by a source, unverified
  • github.com https://github.com/madler/zlib/issues/904 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 2.9 CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
OSV 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
julia Openresty_jll
>=1.21.4+0, <1.29.203+0
1.29.203+0
julia Zlib_jll
>=1.2.12+3, <1.3.2+0
1.3.2+0
julia fmusim_jll
<0.0.39001+0
0.0.39001+0

Affected products

  • zlib zlib

Classification

Weakness
  • CWE-1284 Improper Validation of Specified Quantity in Input

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.