Vulnerability in Zlib
CVE-2026-27171
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 2.9 (Low). Vector: CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L.
EPSS exploit prediction
EPSS: 0.002 (7.5th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 7th percentile — 7.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: -0.000
Affected products
- Zlib — versions 0
Weakness classification (CWE)
References
- github.com/madler/zlib/issues/904 (Exploit, Issue Tracking)
- 7asecurity.com/reports/pentest-report-zlib-RC1.1.pdf (Technical Description)
- 7asecurity.com/blog/2026/02/zlib-7asecurity-audit/ (Product)
- ostif.org/zlib-audit-complete/ (Product)
- github.com/madler/zlib/releases/tag/v1.3.2 (Release Notes)
Frequently asked questions
- What is CVE-2026-27171?
- CVE-2026-27171 is a low-severity vulnerability in Zlib, classified under Improper Validation of Specified Quantity in Input. CVSS score: 2.9/10. Published 2026-02-18.
- How severe is CVE-2026-27171?
- Low severity. CVSS v3 base score is 2.9 out of 10.