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Vulnerability record · CVE-2026-27171 · published 18 February 2026

CVE-2026-27171: Zlib vulnerability

Zlib · Zlib

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.

5.5 CVSS 3.1 Medium EPSS 0.19% · top 92.5% CWE-1284 · CWE-1284
5.5CVSS 3.1 base score
0.19%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
6References, 1 tagged exploit
17 Jun 2026Last modified by NVD

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.

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://7asecurity.com/blog/2026/02/zlib-7asecurity-audit/ Product
https://7asecurity.com/reports/pentest-report-zlib-RC1.1.pdf Technical Description
https://github.com/madler/zlib/issues/904 ExploitIssue Tracking
https://github.com/madler/zlib/releases/tag/v1.3.2 Release Notes
https://ostif.org/zlib-audit-complete/ Product
https://7asecurity.com/reports/pentest-report-zlib-RC1.1.pdf Technical Description

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.8CVE-2023-45853Zlib integer overflow vulnerabilityMiniZip in zlib through 1.3 has an integer overflow and resultant heap-based buffer overflow in zipOpenNewFileInZip4_64 via a long filename, comment,…EPSS 3.2%9.8CVE-2022-37434Zlib out-of-bounds write vulnerabilityzlib through 1.2.12 has a heap-based buffer over-read or buffer overflow in inflate in inflate.c via a large gzip header extra field. NOTE: only appl…EPSS 18%9.8CVE-2016-9841Zlib vulnerabilityinffast.c in zlib 1.2.8 might allow context-dependent attackers to have unspecified impact by leveraging improper pointer arithmetic.EPSS 7.6%9.8CVE-2016-9843Zlib vulnerabilityThe crc32_big function in crc32.c in zlib 1.2.8 might allow context-dependent attackers to have unspecified impact via vectors involving big-endian C…EPSS 5.8%9.8CVE-2002-0059Zlib double free vulnerabilityThe decompression algorithm in zlib 1.1.3 and earlier, as used in many different utilities and packages, causes inflateEnd to release certain memory …EPSS 9.7%8.8CVE-2016-9840Boost vulnerabilityinftrees.c in zlib 1.2.8 might allow context-dependent attackers to have unspecified impact by leveraging improper pointer arithmetic.EPSS 4.8%8.8CVE-2016-9842Zlib vulnerabilityThe inflateMark function in inflate.c in zlib 1.2.8 might allow context-dependent attackers to have unspecified impact via vectors involving left shi…EPSS 5.2%7.5CVE-2018-25032zlib deflate out-of-bounds write on distant matcheszlib before 1.2.12 allows memory corruption when deflating (compressing) input that contains many distant matches, an out-of-bounds write (CWE-787). …EPSS 52%analysed

Source: NIST National Vulnerability Database (record CVE-2026-27171), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.