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openssh — security advisory

Type: advisorySources: OSVAdvisory ID: DEBIAN-CVE-2023-25136

OpenSSH server (sshd) 9.1 introduced a double-free vulnerability during options.kex_algorithms handling. This is fixed in OpenSSH 9.2. The double free can be leveraged, by an unauthenticated remote attacker in the default configuration, to jump to any location in the sshd address space. One third-party report states "remote code execution is theoretically possible."

Products
openssh
Affected versions
Not specified
Fixed versions
1:9.2p1-1
CVEs
CVE-2023-25136
Confirmed fixed CVEs
Not specified
Updated in this feed
1 Nov 2026, 15:45 UTC · Revision 1

Source evidence

DEBIAN-CVE-2023-25136

core-osv · Original source

Published 3 Feb 2023, 06:15 UTC

OpenSSH server (sshd) 9.1 introduced a double-free vulnerability during options.kex_algorithms handling. This is fixed in OpenSSH 9.2. The double free can be leveraged, by an unauthenticated remote attacker in the default configuration, to jump to any location in the sshd address space. One third-party report states "remote code execution is theoretically possible."

osv:DEBIAN-CVE-2023-25136

openssh

Fixed versions: 1:9.2p1-1

openssh

Fixed versions: 1:9.2p1-1

openssh

Fixed versions: 1:9.2p1-1

Complete source record
{
  "id": "c7c0cb0b07149c3a04169f06742685f188a848fb7fb76024d2c986fca4e7d11b",
  "url": "https://osv.dev/vulnerability/DEBIAN-CVE-2023-25136",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "DEBIAN-CVE-2023-25136",
    "summary": "OpenSSH server (sshd) 9.1 introduced a double-free vulnerability during options.kex_algorithms handling. This is fixed in OpenSSH 9.2. The double free can be leveraged, by an unauthenticated remote attacker in the default configuration, to jump to any location in the sshd address space. One third-party report states \"remote code execution is theoretically possible.\"",
    "evidence": "osv:DEBIAN-CVE-2023-25136",
    "products": [
      {
        "name": {
          "value": "openssh",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "1:9.2p1-1",
            "evidence": "/affected/0/ranges"
          }
        ],
        "affected_versions": []
      },
      {
        "name": {
          "value": "openssh",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "1:9.2p1-1",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      },
      {
        "name": {
          "value": "openssh",
          "evidence": "/affected/2/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "1:9.2p1-1",
            "evidence": "/affected/2/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "medium",
    "structured": {
      "id": "DEBIAN-CVE-2023-25136",
      "aliases": [
        "DEBIAN-CVE-2023-25136"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "1:9.2p1-1"
                }
              ]
            }
          ],
          "package": {
            "name": "openssh",
            "purl": "pkg:deb/debian/openssh?arch=source&distro=bookworm",
            "ecosystem": "Debian:12"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2023-25136.json"
          },
          "ecosystem_specific": {
            "urgency": "not yet assigned"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "1:9.2p1-1"
                }
              ]
            }
          ],
          "package": {
            "name": "openssh",
            "purl": "pkg:deb/debian/openssh?arch=source&distro=trixie",
            "ecosystem": "Debian:13"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2023-25136.json"
          },
          "ecosystem_specific": {
            "urgency": "not yet assigned"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "1:9.2p1-1"
                }
              ]
            }
          ],
          "package": {
            "name": "openssh",
            "purl": "pkg:deb/debian/openssh?arch=source&distro=forky",
            "ecosystem": "Debian:14"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2023-25136.json"
          },
          "ecosystem_specific": {
            "urgency": "not yet assigned"
          }
        }
      ],
      "modified": "2026-10-26T18:01:37.169158696Z",
      "provider": "osv",
      "upstream": [
        "CVE-2023-25136"
      ],
      "references": [
        "https://security-tracker.debian.org/tracker/CVE-2023-25136"
      ]
    },
    "related_cves": [
      {
        "value": "CVE-2023-25136",
        "evidence": "/upstream"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 455602,
  "published_at": "2023-02-03T06:15:09.35+00:00"
}