CVE-2026-27820 | ruby zlib up to 3.0.0/3.1.1/3.2.2 zlib::GzipReader buffer overflow (GHSA-g857-hhfv-j68w)

VDB-357947 · CVE-2026-27820 · GHSA-G857-HHFV-J68W RUBY ZLIB UP TO 3.0.0/3.1.1/3.2.2 ZLIB::GZIPREADER BUFFER OVERFLOW HISTORYDIFFRELATEJSONXMLCTI CVSS Meta Temp Score Current Exploit Price (≈) CTI Interest Score 5.1 $0-$5k 1.57+ Summaryinfo A vulnerability identified as critical has been detected in ruby zlib up to 3.0.0/3.1.1/3.2.2. The impacted element is the function zlib::GzipReader. The manipulation leads to buffer overflow. This vulnerability is uniquely identified as CVE-2026-27820. The attack is possible to be carried out remotely. No exploit exists. You should upgrade the affected component. Detailsinfo A vulnerability was found in ruby zlib up to 3.0.0/3.1.1/3.2.2. It has been rated as critical. This issue affects the function zlib::GzipReader. The manipulation with an unknown input leads to a buffer overflow vulnerability. Using CWE to declare the problem leads to CWE-120. The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer, leading to a buffer overflow. Impacted is availability. The summary by CVE is: 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. It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-27820 since 02/24/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details of the vulnerability are known, but there is no available exploit. Upgrading to version 3.0.1, 3.1.2 or 3.2.3 eliminates this vulnerability. Productinfo Type Programming Language Software Vendor ruby Name zlib Version 3.0 3.1.0 3.1.1 3.2.0 3.2.1 3.2.2 License open-source Website Product: https://github.com/ruby/zlib/ CPE 2.3info 🔒 🔒 🔒 CPE 2.2info 🔒 🔒 🔒 CVSSv4info VulDB Vector: 🔒 VulDB Reliability: 🔍 CNA CVSS-B Score: 🔒 CNA CVSS-BT Score: 🔒 CNA Vector: 🔒 CVSSv3info VulDB Meta Base Score: 5.3 VulDB Meta Temp Score: 5.1 VulDB Base Score: 5.3 VulDB Temp Score: 5.1 VulDB Vector: 🔒 VulDB Reliability: 🔍 CVSSv2info Vector Complexity Authentication Confidentiality Integrity Availability Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock VulDB Base Score: 🔒 VulDB Temp Score: 🔒 VulDB Reliability: 🔍 Exploitinginfo Class: Buffer overflow CWE: CWE-120 / CWE-119 CAPEC: 🔒 ATT&CK: 🔒 Physical: No Local: No Remote: Yes Availability: 🔒 Status: Not defined Price Prediction: 🔍 Current Price Estimation: 🔒 0-Day Unlock Unlock Unlock Unlock Today Unlock Unlock Unlock Unlock Threat Intelligenceinfo Interest: 🔍 Active Actors: 🔍 Active APT Groups: 🔍 Countermeasuresinfo Recommended: Upgrade Status: 🔍 0-Day Time: 🔒 Upgrade: zlib 3.0.1/3.1.2/3.2.3 Timelineinfo 02/24/2026 CVE reserved 04/16/2026 +50 days Advisory disclosed 04/16/2026 +0 days VulDB entry created 04/16/2026 +0 days VulDB entry last update Sourcesinfo Product: github.com Advisory: GHSA-g857-hhfv-j68w Status: Confirmed CVE: CVE-2026-27820 (🔒) GCVE (CVE): GCVE-0-2026-27820 GCVE (VulDB): GCVE-100-357947 Entryinfo Created: 04/16/2026 21:20 Changes: 04/16/2026 21:20 (70) Complete: 🔍 Cache ID: 99:629:101 Discussion No comments yet. Languages: en. Please log in to comment. ◂ PreviousOverviewNext ▸