USN-8556-1

It was discovered that the Net::IMAP client in Ruby did not properly sanitize Symbol arguments passed to IMAP commands. A remote attacker controlling a malicious IMAP server, or able to influence command arguments, could use this to inject arbitrary IMAP commands via CRLF sequences. (CVE-2026-42258)

It was discovered that the Zlib::GzipReader in Ruby did not correctly ensure sufficient buffer capacity in the zstreambufferungets function. An attacker could use this to craft a gzip stream that, when processed, could cause a buffer overflow, resulting in memory corruption and possibly arbitrary code execution. (CVE-2026-27820)

References

Affected packages

Ubuntu:Pro:16.04:LTS / ruby2.3

Package

Name: ruby2.3
Purl: pkg:deb/ubuntu/ruby2.3?arch=source&distro=esm-infra-legacy%2Fxenial

Affected ranges

Type: ECOSYSTEM
Events: Introduced

0Unknown introduced version / All previous versions are affected

Fixed

2.3.1-2~ubuntu16.04.16+esm15

Affected versions

2.*

2.3.0-1

2.3.0-2

2.3.0-4ubuntu2

2.3.0-4ubuntu3

2.3.0-5ubuntu1

2.3.1-2~16.04

2.3.1-2~16.04.2

2.3.1-2~16.04.4

2.3.1-2~16.04.5

2.3.1-2~16.04.6

2.3.1-2~16.04.7

2.3.1-2~16.04.9

2.3.1-2~16.04.10

2.3.1-2~16.04.11

2.3.1-2~16.04.12

2.3.1-2~ubuntu16.04.13

2.3.1-2~ubuntu16.04.14

2.3.1-2~ubuntu16.04.15

2.3.1-2~ubuntu16.04.16

2.3.1-2~ubuntu16.04.16+esm1

2.3.1-2~ubuntu16.04.16+esm2

2.3.1-2~ubuntu16.04.16+esm3

2.3.1-2~ubuntu16.04.16+esm4

2.3.1-2~ubuntu16.04.16+esm5

2.3.1-2~ubuntu16.04.16+esm6

2.3.1-2~ubuntu16.04.16+esm7

2.3.1-2~ubuntu16.04.16+esm8

2.3.1-2~ubuntu16.04.16+esm9

2.3.1-2~ubuntu16.04.16+esm10

2.3.1-2~ubuntu16.04.16+esm11

2.3.1-2~ubuntu16.04.16+esm12

2.3.1-2~ubuntu16.04.16+esm14

Ecosystem specific

{
    "binaries": [
        {
            "binary_version": "2.3.1-2~ubuntu16.04.16+esm15",
            "binary_name": "libruby2.3"
        },
        {
            "binary_version": "2.3.1-2~ubuntu16.04.16+esm15",
            "binary_name": "ruby2.3"
        },
        {
            "binary_version": "2.3.1-2~ubuntu16.04.16+esm15",
            "binary_name": "ruby2.3-tcltk"
        }
    ],
    "availability": "Available with Ubuntu Pro with Legacy support add-on: https://ubuntu.com/pro"
}

Database specific

source

"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/usn/USN-8556-1.json"

cves_map

{
    "cves": [
        {
            "severity": [
                {
                    "score": "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",
                    "type": "CVSS_V4"
                },
                {
                    "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
                    "type": "CVSS_V3"
                },
                {
                    "score": "medium",
                    "type": "Ubuntu"
                }
            ],
            "id": "CVE-2026-27820"
        },
        {
            "severity": [
                {
                    "score": "CVSS:4.0/AV:L/AC:H/AT:P/PR:N/UI:P/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N",
                    "type": "CVSS_V4"
                },
                {
                    "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:H/A:N",
                    "type": "CVSS_V3"
                },
                {
                    "score": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:L",
                    "type": "CVSS_V3"
                },
                {
                    "score": "medium",
                    "type": "Ubuntu"
                }
            ],
            "id": "CVE-2026-42258"
        }
    ],
    "ecosystem": "Ubuntu:Pro:16.04:LTS"
}