CVE-2026-27820 (GCVE-0-2026-27820)
Vulnerability from cvelistv5 – Published: 2026-04-16 17:27 – Updated: 2026-04-16 18:20
VLAI
EPSS
VEX
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
SSVC
Exploitation: none
Automatable: yes
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-04-16 18:20 UTC
CWE
Assigner
References
2 references
| URL | Tags |
|---|---|
| https://github.com/ruby/zlib/security/advisories/… | x_refsource_CONFIRM |
| https://hackerone.com/reports/3467067 | x_refsource_MISC |
Impacted products
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Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
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