Buffer overflow in zlib - CVE-2026-27820
Published: April 21, 2026 / Updated: April 21, 2026
Vulnerability identifier: #VU126646
CSH Severity: High
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N/E:U/U:Amber
CVE-ID: CVE-2026-27820
CWE-ID: CWE-120
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Ruby
Affected software:
zlib
zlib
Detailed vulnerability description
The vulnerability allows a remote attacker to cause memory corruption.
The vulnerability exists due to buffer overflow in zstream_buffer_ungets() function when parsing input within the Zlib::GzipReader. A remote attacker can provide crafted input that causes the buffer length to exceed its capacity to cause memory corruption.
User interaction is required.
How to mitigate CVE-2026-27820
Install security update from vendor's website.