zlib is a Ruby interface for the zlib compression/decompression library. Versions 3.0.0 and below, 3.1.0, 3.1.1, 3.2.0 and 3.2.1 contain a buffer overflow vulnerability in the Zlib::GzipReader. The zstream_buffer_ungets function prepends caller-provided bytes ahead of previously produced output but fails to guarantee the backing Ruby string has enough capacity before the memmove shifts the existing data. This can lead to memory corruption when the buffer length exceeds capacity. This issue has been fixed in versions 3.0.1, 3.1.2 and 3.2.3.
History

Thu, 16 Apr 2026 19:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Thu, 16 Apr 2026 18:00:00 +0000

Type Values Removed Values Added
Description zlib is a Ruby interface for the zlib compression/decompression library. Versions 3.0.0 and below, 3.1.0, 3.1.1, 3.2.0 and 3.2.1 contain a buffer overflow vulnerability in the Zlib::GzipReader. The zstream_buffer_ungets function prepends caller-provided bytes ahead of previously produced output but fails to guarantee the backing Ruby string has enough capacity before the memmove shifts the existing data. This can lead to memory corruption when the buffer length exceeds capacity. This issue has been fixed in versions 3.0.1, 3.1.2 and 3.2.3.
Title zlib: Buffer Overflow in Zlib::GzipReader ungetc via large input leads to memory corruption
Weaknesses CWE-120
CWE-131
References
Metrics cvssV4_0

{'score': 1.7, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U'}


cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-04-16T18:20:21.451Z

Reserved: 2026-02-24T02:32:39.799Z

Link: CVE-2026-27820

cve-icon Vulnrichment

Updated: 2026-04-16T18:20:15.404Z

cve-icon NVD

Status : Received

Published: 2026-04-16T18:16:44.770

Modified: 2026-04-16T18:16:44.770

Link: CVE-2026-27820

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.