golang-refraction-networking-utls — security advisory

{
  "id": "d355349eedbb9dde8f7c60df48c419b95dbf28ebf50ec86ea119879ff0e02e80",
  "url": "https://osv.dev/vulnerability/UBUNTU-CVE-2026-26994",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "UBUNTU-CVE-2026-26994",
    "summary": "uTLS is a fork of crypto/tls, created to customize ClientHello for fingerprinting resistance while still using it for the handshake. In versions 1.6.7 and below, uTLS did not implement the TLS 1.3 downgrade protection mechanism specified in RFC 8446 Section 4.1.3 when using a uTLS ClientHello spec. This allowed an active network adversary to downgrade TLS 1.3 connections initiated by a uTLS client to a lower TLS version (e.g., TLS 1.2) by modifying the ClientHello message to exclude the SupportedVersions extension, causing the server to respond with a TLS 1.2 ServerHello (along with a downgrade canary in the ServerHello random field). Because uTLS did not check the downgrade canary in the ServerHello random field, clients would accept the downgraded connection without detecting the attack. This attack could also be used by an active network attacker to fingerprint uTLS connections. This issue has been fixed in version 1.7.0.",
    "evidence": "osv:UBUNTU-CVE-2026-26994",
    "products": [
      {
        "name": {
          "value": "golang-refraction-networking-utls",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": [
          {
            "value": "0.0~git20201210.2179f28-1",
            "evidence": "/affected/0/versions"
          }
        ]
      },
      {
        "name": {
          "value": "golang-refraction-networking-utls",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": [
          {
            "value": "1.2.1-2",
            "evidence": "/affected/1/versions"
          }
        ]
      },
      {
        "name": {
          "value": "golang-refraction-networking-utls",
          "evidence": "/affected/2/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": [
          {
            "value": "1.2.1-3.1",
            "evidence": "/affected/2/versions"
          }
        ]
      },
      {
        "name": {
          "value": "golang-refraction-networking-utls",
          "evidence": "/affected/3/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": [
          {
            "value": "1.2.1-3.1",
            "evidence": "/affected/3/versions"
          }
        ]
      },
      {
        "name": {
          "value": "golang-refraction-networking-utls",
          "evidence": "/affected/4/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": [
          {
            "value": "1.2.1-3.1",
            "evidence": "/affected/4/versions"
          }
        ]
      }
    ],
    "severity": "medium",
    "structured": {
      "id": "UBUNTU-CVE-2026-26994",
      "aliases": [
        "UBUNTU-CVE-2026-26994"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N"
        },
        {
          "type": "Ubuntu",
          "score": "medium"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                }
              ]
            }
          ],
          "package": {
            "name": "golang-refraction-networking-utls",
            "purl": "pkg:deb/ubuntu/golang-refraction-networking-utls?arch=source&distro=jammy",
            "ecosystem": "Ubuntu:22.04:LTS"
          },
          "versions": [
            "0.0~git20201210.2179f28-1"
          ],
          "database_specific": {
            "source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-26994.json"
          },
          "ecosystem_specific": {
            "binaries": [
              {
                "binary_name": "golang-refraction-networking-utls-dev",
                "binary_version": "0.0~git20201210.2179f28-1"
              }
            ]
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                }
              ]
            }
          ],
          "package": {
            "name": "golang-refraction-networking-utls",
            "purl": "pkg:deb/ubuntu/golang-refraction-networking-utls?arch=source&distro=noble",
            "ecosystem": "Ubuntu:24.04:LTS"
          },
          "versions": [
            "1.2.1-2"
          ],
          "database_specific": {
            "source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-26994.json"
          },
          "ecosystem_specific": {
            "binaries": [
              {
                "binary_name": "golang-refraction-networking-utls-dev",
                "binary_version": "1.2.1-2"
              }
            ]
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                }
              ]
            }
          ],
          "package": {
            "name": "golang-refraction-networking-utls",
            "purl": "pkg:deb/ubuntu/golang-refraction-networking-utls?arch=source&distro=questing",
            "ecosystem": "Ubuntu:25.10"
          },
          "versions": [
            "1.2.1-3.1"
          ],
          "database_specific": {
            "source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-26994.json"
          },
          "ecosystem_specific": {
            "binaries": [
              {
                "binary_name": "golang-refraction-networking-utls-dev",
                "binary_version": "1.2.1-3.1"
              }
            ]
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                }
              ]
            }
          ],
          "package": {
            "name": "golang-refraction-networking-utls",
            "purl": "pkg:deb/ubuntu/golang-refraction-networking-utls?arch=source&distro=stonking",
            "ecosystem": "Ubuntu:26.10"
          },
          "versions": [
            "1.2.1-3.1"
          ],
          "database_specific": {
            "source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-26994.json"
          },
          "ecosystem_specific": {
            "binaries": [
              {
                "binary_name": "golang-refraction-networking-utls-dev",
                "binary_version": "1.2.1-3.1"
              }
            ]
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                }
              ]
            }
          ],
          "package": {
            "name": "golang-refraction-networking-utls",
            "purl": "pkg:deb/ubuntu/golang-refraction-networking-utls?arch=source&distro=resolute",
            "ecosystem": "Ubuntu:26.04:LTS"
          },
          "versions": [
            "1.2.1-3.1"
          ],
          "database_specific": {
            "source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-26994.json"
          },
          "ecosystem_specific": {
            "binaries": [
              {
                "binary_name": "golang-refraction-networking-utls-dev",
                "binary_version": "1.2.1-3.1"
              }
            ]
          }
        }
      ],
      "modified": "2026-10-17T12:58:48.704604015Z",
      "provider": "osv",
      "upstream": [
        "CVE-2026-26994"
      ],
      "references": [
        "https://ubuntu.com/security/CVE-2026-26994",
        "https://www.cve.org/CVERecord?id=CVE-2026-26994",
        "https://github.com/refraction-networking/utls/security/advisories/GHSA-pmc3-p9hx-jq96",
        "https://github.com/refraction-networking/utls/commit/f8892761e2a4d29054264651d3a86fda83bc83f9",
        "https://github.com/refraction-networking/utls/issues/181",
        "https://github.com/refraction-networking/utls/pull/337"
      ]
    },
    "related_cves": [
      {
        "value": "CVE-2026-26994",
        "evidence": "/upstream"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 359076,
  "published_at": "2026-02-20T03:16:00+00:00"
}