---
cve: "CVE-2026-64194"
severity: "HIGH"
cvss: 7.5
epss: "42%"
vendor: "NLNETLABS"
kev: false
exploited: false
published: "2026-07-20 19:17:30"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-09-03T04:54:14+02:00"
---

# CVE-2026-64194

> 7.5 HIGH

## Beschreibung

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.

## CVSS-Vektor

```
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Gering | bad |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |
| S Scope | Unverändert | good |
| C Vertraulichkeit | Keine | good |
| I Integrität | Keine | good |
| A Verfügbarkeit | Hoch | bad |

## Referenzen

- <https://www.net-dns.org/blog/#release-candidate-for-netdns-1.56>
- <https://rt.cpan.org/Ticket/Display.html?id=179946>
- <https://metacpan.org/release/NLNETLABS/Net-DNS-1.55_01/changes>
- <http://www.openwall.com/lists/oss-security/2026/07/20/13>
- <https://lists.debian.org/debian-lts-announce/2026/08/msg00052.html>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-64194) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_