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
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
ruby zlib Affected: < 3.0.1
Affected: >= 3.1.0, < 3.1.2
Affected: >= 3.2.0, < 3.2.3
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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



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