{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 4.2.14.Final"
      },
      "package": {
        "ecosystem": "Maven",
        "name": "io.netty:netty-resolver-dns"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "4.2.0.Final"
            },
            {
              "fixed": "4.2.15.Final"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 4.1.134.Final"
      },
      "package": {
        "ecosystem": "Maven",
        "name": "io.netty:netty-resolver-dns"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "4.1.135.Final"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-45673"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-330",
      "CWE-340"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-08T23:02:05Z",
    "nvd_published_at": "2026-06-12T15:16:27Z",
    "severity": "MODERATE"
  },
  "details": "### Summary\nNetty\u0027s DNS resolver uses a predictable PRNG for generating DNS transaction IDs and defaults to a static UDP source port. This combination reduces the entropy of DNS queries, enabling DNS Cache Poisoning (Kaminsky attack).\n\n### Details\nTwo factors contribute to this vulnerability in io.netty.resolver.dns:\n- Predictable Query IDs: `DnsQueryIdSpace` manages 16-bit transaction IDs in buckets of 16,384 IDs. It initializes only the first bucket. When an ID is returned, it is pushed back into the bucket at a random index generated by java.util.concurrent.ThreadLocalRandom:\n\n```java\nRandom random = ThreadLocalRandom.current();\nint insertionPosition = random.nextInt(count + 1);\n```\n\nBecause ThreadLocalRandom is a predictable LCG and the resolver operates within a single bucket, the sequence of IDs is predictable once the PRNG state is mathematically recovered.\n\n- Default Static Source Port: `DnsNameResolverBuilder` defaults to a `channelStrategy` of `ChannelPerResolver`. This binds the DatagramChannel once, resulting in a static source port for all subsequent queries.\n\nCombined, a static source port and predictable transaction IDs reduces the entropy required to secure DNS resolution against spoofing.\n\n### Impact\nDNS Cache Poisoning. Downstream applications using the default Netty DNS resolver may connect to malicious IPs, leading to traffic interception or MitM attacks.",
  "id": "GHSA-xmv7-r254-6q78",
  "modified": "2026-06-12T19:29:30Z",
  "published": "2026-06-08T23:02:05Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/netty/netty/security/advisories/GHSA-xmv7-r254-6q78"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-45673"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/netty/netty"
    },
    {
      "type": "WEB",
      "url": "https://github.com/netty/netty/releases/tag/netty-4.1.135.Final"
    },
    {
      "type": "WEB",
      "url": "https://github.com/netty/netty/releases/tag/netty-4.2.15.Final"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Netty: DNS Cache Poisoning due to Predictable PRNG and Default Static Source Port"
}