CVE-2026-27820 (GCVE-0-2026-27820)

Vulnerability from cvelistv5 – Published: 2026-04-16 17:27 – Updated: 2026-04-16 18:20
VLAI
Title
zlib: Buffer Overflow in Zlib::GzipReader ungetc via large input leads to memory corruption
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.
Severity
1.7 (Low)
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
SSVC
Exploitation: none Automatable: yes Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-04-16 18:20 UTC
CWE
  • CWE-120 - Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
  • CWE-131 - Incorrect Calculation of Buffer Size
Assigner
References
Impacted products
Vendor Product Version CPE status
ruby zlib Affected: < 3.0.1
Affected: >= 3.1.0, < 3.1.2
Affected: >= 3.2.0, < 3.2.3
guessed Create a notification for this product.
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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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