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TI-2026-21613 Aliases CVE-2026-27171GHSA-h858-mf2m-8jf4

zlib before 1.3.2 allows CPU consumption via crc32_combine64 and crc32_combine_gen64…

Priority MEDIUM 58CWE-1284Published · Updated

Key facts

Attack vector
Local
Privileges required
Low
User interaction
None
Attack complexity
Low
Impact type
—
Confidentiality · integrity · availability
None · None · High
Fix status
Partial Red Hat: 14 without a fix

Attack profile from CVSS 3.1 · NVD. Fix status from CNA and Red Hat.

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00248 16th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Partial zlib (zlib): 1.3.2Red Hat: 14 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
zlibzlibbefore 1.3.21.3.2Patch availableCNA
  • zlib Vendorzlib Affected before 1.3.2 Fixed in 1.3.2 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:zlib:zlib:*:*:*:*:*:*:*:*1.2.12 to before 1.3.2Vulnerablezlib
  • cpe:2.3:a:zlib:zlib:*:*:*:*:*:*:*:* Versions 1.2.12 to before 1.3.2 Vulnerable ·zlib

Remediation

  • Fix · CNA zlib (zlib) Fixed in 1.3.2

Vendor assessments

Red Hat

Red Hat rating: Low. Red Hat's page for this CVE →

ProductStatusPlan or fix
Logging Subsystem for Red Hat OpenShiftAffectedNo fix planned: Out of support scope
Red Hat Enterprise Linux 10AffectedNo fix yet: Fix deferred
Red Hat Enterprise Linux 6AffectedNo fix planned: Out of support scope
Red Hat Enterprise Linux 7AffectedNo fix yet: Fix deferred
Red Hat Enterprise Linux 8AffectedNo fix yet: Fix deferred
Red Hat Enterprise Linux 9AffectedNo fix yet: Fix deferred
Red Hat JBoss Core ServicesAffectedNo fix yet: Fix deferred
Red Hat OpenShift AI (RHOAI)Affected—
Red Hat OpenShift Container Platform 4AffectedNo fix yet: Fix deferred
Red Hat build of OpenJDK 1.8AffectedNo fix yet: Fix deferred
Red Hat build of OpenJDK 11 ELSAffectedNo fix planned: Out of support scope
Red Hat build of OpenJDK 17AffectedNo fix yet: Fix deferred
Red Hat build of OpenJDK 21AffectedNo fix yet: Fix deferred
Red Hat build of OpenJDK 25AffectedNo fix yet: Fix deferred
Not affected: 4 products
  • Red Hat Enterprise Linux 10
  • Red Hat Enterprise Linux 8
  • Red Hat Enterprise Linux 9
  • Red Hat OpenShift AI (RHOAI)

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-27171
  2. 2026-10-03 Alias added: GHSA-h858-mf2m-8jf4
  3. 2026-11-06 Affected versions changed · Red Hat

References

Exploit 1

Other 4

  • TI-2022-17498 zlib through 1.2.12 has a heap-based buffer over-read or buffer overflow in inflate in… CVSS 3.1CRITICAL 9.8
  • TI-2018-15259 zlib before 1.2.12 allows memory corruption when deflating (i.e., when compressing) if… CVSS 3.1HIGH 7.5
  • TI-2026-17794 zlib <= 1.3.1.2 untgz Global Buffer Overflow in TGZfname() CVSS 4.0MEDIUM 4.6
  • TI-2016-07970 inffast.c in zlib 1.2.8 might allow context-dependent attackers to have unspecified… CVSS 3.1CRITICAL 9.8
  • TI-2003-00102 Buffer overflow in the gzprintf function in zlib 1.1.4, when zlib is compiled without… CVSS 2.0HIGH 7.5
  • TI-2002-00055 The decompression algorithm in zlib 1.1.3 and earlier, as used in many different… CVSS 3.1CRITICAL 9.8
See all 13 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences