---
id: CVE-2026-64194
title: >-
  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
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 …
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-674
published: '2026-07-20'
updated: '2026-08-30'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-64194'
references:
  - url: 'https://metacpan.org/release/NLNETLABS/Net-DNS-1.55_01/changes'
    label: 9b29abf9-4ab0-4765-b253-1875cd9b441e
  - url: 'https://rt.cpan.org/Ticket/Display.html?id=179946'
    label: 9b29abf9-4ab0-4765-b253-1875cd9b441e
  - url: 'https://www.net-dns.org/blog/#release-candidate-for-netdns-1.56'
    label: 9b29abf9-4ab0-4765-b253-1875cd9b441e
  - url: 'http://www.openwall.com/lists/oss-security/2026/07/20/13'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://lists.debian.org/debian-lts-announce/2026/08/msg00052.html'
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
epss: 0.0068
epssPercentile: 0.50326
ingestedAt: '2026-08-30T21:58:10.818Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.