FKIE_CVE-2026-64194

Vulnerability from fkie_nvd - Published: 2026-07-20 19:17 - Updated: 2026-07-20 21:16
Severity
Summary
Net::DNS versions through 1.55 for Perl allow Denial of Service via deep DNS compression pointer chains. Net::DNS::DomainName::decode follows RFC 1035 compression pointers by recursing into itself with no depth limit. It is possible to construct a name which saturates the call stack (at least with larger TCP responses), leading to a potential Denial of Service. The guard `$link < $offset` prevents forward and circular chains, but still allows arbitrarily long backward chains. The per-offset cache (`$cache`) is populated at the start of each call and short-circuits only re-traverses of the same offset - the initial descent through a fresh chain still recurses at full depth. A crafted packet can chain two-byte compression pointers so that each one points two bytes earlier than the previous, producing a chain length of `offset / 2`. For the 14-bit pointer field (max offset 16383) this gives up to ~8191 recursive frames. For a TCP DNS message the limit is the 16-bit length field (~32767 frames). Perl's default C stack handles only a few thousand frames; beyond that the process receives SIGSEGV or similar, which is a denial-of-service for any application parsing untrusted DNS data. The vulnerability is triggered by `Net::DNS::Packet->new(\$wire)` i.e. any point where the library decodes a DNS message from the network.
References
9b29abf9-4ab0-4765-b253-1875cd9b441ehttps://metacpan.org/release/NLNETLABS/Net-DNS-1.55_01/changes
9b29abf9-4ab0-4765-b253-1875cd9b441ehttps://rt.cpan.org/Ticket/Display.html?id=179946
9b29abf9-4ab0-4765-b253-1875cd9b441ehttps://www.net-dns.org/blog/#release-candidate-for-netdns-1.56
af854a3a-2127-422b-91ae-364da2661108http://www.openwall.com/lists/oss-security/2026/07/20/13
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "collectionURL": "https://cpan.org/modules",
          "defaultStatus": "unaffected",
          "packageName": "Net-DNS",
          "product": "Net::DNS",
          "programFiles": [
            "lib/Net/DNS/DomainName.pm"
          ],
          "programRoutines": [
            {
              "name": "Net::DNS::DomainName::decode"
            }
          ],
          "repo": "https://www.net-dns.org/svn/net-dns/",
          "vendor": "NLNETLABS",
          "versions": [
            {
              "lessThanOrEqual": "1.55",
              "status": "affected",
              "version": "0",
              "versionType": "custom"
            }
          ]
        }
      ],
      "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Net::DNS versions through 1.55 for Perl allow Denial of Service via deep DNS compression pointer chains.\n\nNet::DNS::DomainName::decode follows RFC 1035 compression pointers by recursing into itself with no depth limit. It is possible to construct a name which saturates the call stack (at least with larger TCP responses), leading to a potential Denial of Service.\n\nThe guard `$link \u003c $offset` prevents forward and circular chains, but still allows arbitrarily long backward chains. The per-offset cache (`$cache`) is populated at the start of each call and short-circuits only re-traverses of the same offset - the initial descent through a fresh chain still recurses at full depth.\n\nA crafted packet can chain two-byte compression pointers so that each one points two bytes earlier than the previous, producing a chain length of `offset / 2`. For the 14-bit pointer field (max offset 16383) this gives up to ~8191 recursive frames. For a TCP DNS message the limit is the 16-bit length field (~32767 frames). Perl\u0027s default C stack handles only a few thousand frames; beyond that the process receives SIGSEGV or similar, which is a denial-of-service for any application parsing untrusted DNS data.\n\nThe vulnerability is triggered by `Net::DNS::Packet-\u003enew(\\$wire)` i.e. any point where the library decodes a DNS message from the network."
    }
  ],
  "id": "CVE-2026-64194",
  "lastModified": "2026-07-20T21:16:50.320",
  "metrics": {},
  "published": "2026-07-20T19:17:30.157",
  "references": [
    {
      "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
      "url": "https://metacpan.org/release/NLNETLABS/Net-DNS-1.55_01/changes"
    },
    {
      "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
      "url": "https://rt.cpan.org/Ticket/Display.html?id=179946"
    },
    {
      "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
      "url": "https://www.net-dns.org/blog/#release-candidate-for-netdns-1.56"
    },
    {
      "source": "af854a3a-2127-422b-91ae-364da2661108",
      "url": "http://www.openwall.com/lists/oss-security/2026/07/20/13"
    }
  ],
  "sourceIdentifier": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
  "vulnStatus": "Received",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-674"
        }
      ],
      "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
      "type": "Secondary"
    }
  ]
}



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