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

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Summary

CVECVE-2026-64194
StatePUBLISHED
AssignerCPANSec
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-20 19:17:30 UTC
Updated2026-07-20 21:16:50 UTC
DescriptionNet::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.

Risk And Classification

Problem Types: CWE-674 | CWE-674 CWE-674 Uncontrolled Recursion

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA NLNETLABS NetDNS affected 1.55 custom Not specified

References

ReferenceSourceLinkTags
www.openwall.com/lists/oss-security/2026/07/20/13 af854a3a-2127-422b-91ae-364da2661108 www.openwall.com
www.net-dns.org/blog 9b29abf9-4ab0-4765-b253-1875cd9b441e www.net-dns.org
metacpan.org/release/NLNETLABS/Net-DNS-1.55_01/changes 9b29abf9-4ab0-4765-b253-1875cd9b441e metacpan.org
rt.cpan.org/Ticket/Display.html 9b29abf9-4ab0-4765-b253-1875cd9b441e rt.cpan.org
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Steffen Ullrich (en)

Additional Advisory Data

SourceTimeEvent
CNA2026-07-10T00:00:00.000ZIssue reported publicly via RT.
CNA2026-07-10T00:00:00.000ZVersion 1.55_01 (release candidate for version 1.56) published on CPAN.
CNA2026-07-18T00:00:00.000ZVersion 1.56 published on CPAN.

Solutions

CNA: Upgrade to version 1.56 or later.

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