USN-8556-1 (UBUNTU-CVE-2026-27820)

Vulnerability from osv_ubuntu – Published: 2026-07-16 13:54 – Updated: 2026-07-16 13:54 – Source website
VLAI
Summary
ruby2.3 vulnerabilities
Details

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 zstream_buffer_ungets 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
To clipboard 

{
  "affected": [
    {
      "database_specific": {
        "cves_map": {
          "cves": [
            {
              "id": "CVE-2026-27820",
              "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-2026-42258",
              "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"
                }
              ]
            }
          ],
          "ecosystem": "Ubuntu:Pro:16.04:LTS"
        }
      },
      "ecosystem_specific": {
        "availability": "Available with Ubuntu Pro with Legacy support add-on: https://ubuntu.com/pro",
        "binaries": [
          {
            "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",
            "binary_version": "2.3.1-2~ubuntu16.04.16+esm15"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:16.04:LTS",
        "name": "ruby2.3",
        "purl": "pkg:deb/ubuntu/ruby2.3@2.3.1-2~ubuntu16.04.16+esm15?arch=source\u0026distro=esm-infra-legacy/xenial"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.3.1-2~ubuntu16.04.16+esm15"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "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"
      ]
    }
  ],
  "aliases": [],
  "details": "It was discovered that the Net::IMAP client in Ruby did not properly\nsanitize Symbol arguments passed to IMAP commands. A remote attacker\ncontrolling a malicious IMAP server, or able to influence command\narguments, could use this to inject arbitrary IMAP commands via CRLF\nsequences. (CVE-2026-42258)\n\nIt was discovered that the Zlib::GzipReader in Ruby did not correctly\nensure sufficient buffer capacity in the zstream_buffer_ungets function.\nAn attacker could use this to craft a gzip stream that, when processed,\ncould cause a buffer overflow, resulting in memory corruption and possibly\narbitrary code execution. (CVE-2026-27820)",
  "id": "USN-8556-1",
  "modified": "2026-07-16T13:54:42Z",
  "published": "2026-07-16T13:54:42Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://ubuntu.com/security/notices/USN-8556-1"
    },
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-27820"
    },
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-42258"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "summary": "ruby2.3 vulnerabilities",
  "upstream": [
    "UBUNTU-CVE-2026-27820",
    "UBUNTU-CVE-2026-42258"
  ]
}



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