Vulnerability-Lookup

GHSA-M3GJ-74X3-VC94

Vulnerability from github – Published: 2026-07-20 21:31 – Updated: 2026-07-20 21:31

Details

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.

Show details on source website

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{
  "affected": [],
  "aliases": [
    "CVE-2026-64194"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-674"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-07-20T19:17:30Z",
    "severity": null
  },
  "details": "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": "GHSA-m3gj-74x3-vc94",
  "modified": "2026-07-20T21:31:50Z",
  "published": "2026-07-20T21:31:50Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-64194"
    },
    {
      "type": "WEB",
      "url": "https://metacpan.org/release/NLNETLABS/Net-DNS-1.55_01/changes"
    },
    {
      "type": "WEB",
      "url": "https://rt.cpan.org/Ticket/Display.html?id=179946"
    },
    {
      "type": "WEB",
      "url": "https://www.net-dns.org/blog/#release-candidate-for-netdns-1.56"
    },
    {
      "type": "WEB",
      "url": "http://www.openwall.com/lists/oss-security/2026/07/20/13"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

CVE-2026-64194 (GCVE-0-2026-64194)

Vulnerability from cvelistv5 – Published: 2026-07-20 17:55 – Updated: 2026-07-20 20:30

Title

Net::DNS versions through 1.55 for Perl allow Denial of Service via deep DNS compression pointer chains

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.

Severity

No CVSS data available.

CWE

CWE-674 - Uncontrolled Recursion

Assigner

CPANSec

References

4 references

URL	Tags
https://www.net-dns.org/blog/#release-candidate-f…
https://rt.cpan.org/Ticket/Display.html?id=179946	issue-tracking
https://metacpan.org/release/NLNETLABS/Net-DNS-1.…	release-notes
http://www.openwall.com/lists/oss-security/2026/0…

Impacted products

1 product

Vendor	Product	Version
NLNETLABS	Net::DNS	Affected: 0 , ≤ 1.55 (custom)

Credits

Steffen Ullrich

Show details on NVD website

JSON

To clipboard

{
  "containers": {
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      {
        "providerMetadata": {
          "dateUpdated": "2026-07-20T20:30:05.425Z",
          "orgId": "af854a3a-2127-422b-91ae-364da2661108",
          "shortName": "CVE"
        },
        "references": [
          {
            "url": "http://www.openwall.com/lists/oss-security/2026/07/20/13"
          }
        ],
        "title": "CVE Program Container"
      }
    ],
    "cna": {
      "affected": [
        {
          "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"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "reporter",
          "value": "Steffen Ullrich"
        }
      ],
      "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."
        }
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          "descriptions": [
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          "url": "https://www.net-dns.org/blog/#release-candidate-for-netdns-1.56"
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          "url": "https://rt.cpan.org/Ticket/Display.html?id=179946"
        },
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          "tags": [
            "release-notes"
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          "url": "https://metacpan.org/release/NLNETLABS/Net-DNS-1.55_01/changes"
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      ],
      "solutions": [
        {
          "lang": "en",
          "value": "Upgrade to version 1.56 or later."
        }
      ],
      "source": {
        "discovery": "UNKNOWN"
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          "time": "2026-07-10T00:00:00.000Z",
          "value": "Issue reported publicly via RT."
        },
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          "lang": "en",
          "time": "2026-07-10T00:00:00.000Z",
          "value": "Version 1.55_01 (release candidate for version 1.56) published on CPAN."
        },
        {
          "lang": "en",
          "time": "2026-07-18T00:00:00.000Z",
          "value": "Version 1.56 published on CPAN."
        }
      ],
      "title": "Net::DNS versions through 1.55 for Perl allow Denial of Service via deep DNS compression pointer chains",
      "x_generator": {
        "engine": "cpansec-cna-tool 0.1"
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  "cveMetadata": {
    "assignerOrgId": "9b29abf9-4ab0-4765-b253-1875cd9b441e",
    "assignerShortName": "CPANSec",
    "cveId": "CVE-2026-64194",
    "datePublished": "2026-07-20T17:55:05.169Z",
    "dateReserved": "2026-07-19T10:13:00.756Z",
    "dateUpdated": "2026-07-20T20:30:05.425Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
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}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

GHSA-M3GJ-74X3-VC94

CVE-2026-64194 (GCVE-0-2026-64194)

Tags

Sightings

Nomenclature