Buffer Overflow in Zlib::GzipReader ungetc via large input leads to memory corruption

Details A buffer overflow vulnerability exists in Zlib::GzipReader. The zstreambufferungets 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...

Buffer overflow vulnerability in Zlib::GzipReader

A buffer overflow vulnerability exists in Zlib::GzipReader. This vulnerability has been assigned the CVE identifier CVE-2026-27820. We recommend upgrading the zlib gem. Details The zstreambufferungets function prepends caller-provided bytes ahead of previously produced output but fails to guarant...