CVE-2026-27820
Severity CVSS v4.0:
LOW
Type:
CWE-120
Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
Publication date:
16/04/2026
Last modified:
17/04/2026
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.