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Fencer Vulns
high 7.5

CVE-2026-64194 json

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

published 2026-07-20 3 mo ago modified 2026-10-24 15 d ago also EUVD-2026-46052

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.7%
EPSS 0.7% chance of exploitation in 30 days, percentile 52%
public exploits
0
none known

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.

Patch / fix

  • libnet-dns-perl Debian 12 1.36-1+deb12u1
  • libnet-dns-perl Debian 13 1.56-0+deb13u1
  • libnet-dns-perl Debian 14 1.56-1

debian advisories DEBIAN-CVE-2026-64194

  • perl-Net-DNS SLES for SAP 15 SP6, SLES for SAP 15 SP5, SLES for SAP 15 SP4 +8 more 1.14-150000.3.3.1
  • perl-Net-DNS SLES LTSS Extended Security 12 SP5, SLES 12 SP5-LTSS 0.73-5.3.1

suse advisories SUSE-SU-2026:3456-1SUSE-SU-2026:3431-1

  • perl-Net-DNS openSUSE Leap 16.0 1.570.0-bp160.1.1
  • perl-Net-DNS openSUSE Tumbleweed 1.560.0-1.1
  • perl-Net-DNS openSUSE Leap 16.0 1.460.0-bp160.2.1

opensuse advisories openSUSE-SU-2026:21859-1openSUSE-SU-2026:11396-1openSUSE-SU-2026:21437-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-64194 updated cvss 5.9

Net::DNS: Net::DNS: Denial of Service via crafted DNS compression pointers

  • Red Hat Enterprise Linux 7 perl-Net-DNS, perl-Net-DNS-Nameserver
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 8 perl-Net-DNS Red Hat Enterprise Linux 9 perl-Net-DNS, perl-Net-DNS-Nameserver
    affected: no fix available “Fix deferred”
  • Red Hat Enterprise Linux 6 perl-Net-DNS, perl-Net-DNS-Nameserver
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
3 mo ago

Exploit prediction

0.68% chance of exploitation in the next 30 days, higher than 52% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CISA ADP 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

  • NLNETLABS Net::DNS

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.