cvedb.io
CVE-2026-27820
CRITICAL · CVSS 9.8
EPSS exploitation probability: 0%
Published 2026-04-16T18:16:44.770 · Last modified 2026-06-17T10:27:44.400

Summary

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.

Affected products

ruby-lang — zlib

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References

This product uses data from the NVD API but is not endorsed or certified by the NVD. Informational only; not professional security advice.