Buffer Overflow Vulnerability in zlib Ruby Interface from Ruby
CVE-2026-27820

1.7LOW

Key Information:

Vendor

Ruby

Status
Zlib
Vendor
CVE Published:
16 April 2026

What is CVE-2026-27820?

A buffer overflow vulnerability exists in the zlib Ruby interface, specifically in the Zlib::GzipReader. The flaw lies within the zstream_buffer_ungets function, as it incorrectly handles input bytes, potentially leading to memory corruption when the data being written exceeds the available buffer capacity. This issue has been addressed in the updates with versions 3.0.1, 3.1.2, and 3.2.3, which remedy the flawed memory handling.

Affected Version(s)

zlib < 3.0.1 < 3.0.1

zlib >= 3.1.0, < 3.1.2 < 3.1.0, 3.1.2

zlib >= 3.2.0, < 3.2.3 < 3.2.0, 3.2.3

References

https://github.com/ruby/zlib/security/advisories/GHSA-g85...
x_refsource_CONFIRM
https://hackerone.com/reports/3467067
x_refsource_MISC

CVSS V4

Score:
1.7
Severity:
LOW
Confidentiality:
None
Integrity:
None
Availability:
Low
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
Physical
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • Vulnerability published

  • Vulnerability Reserved

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