======================================================================== CVE-2026-64194 CPAN Security Group ======================================================================== CVE ID: CVE-2026-64194 Distribution: Net-DNS Versions: through 1.55 MetaCPAN: https://metacpan.org/dist/Net-DNS VCS Repo: https://www.net-dns.org/svn/net-dns/ Net::DNS versions through 1.55 for Perl allow Denial of Service via deep DNS compression pointer chains Description ----------- 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. Problem types ------------- - CWE-674 Uncontrolled Recursion Solutions --------- Upgrade to version 1.56 or later. References ---------- 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 Timeline -------- - 2026-07-10: Issue reported publicly via RT. - 2026-07-10: Version 1.55_01 (release candidate for version 1.56) published on CPAN. - 2026-07-18: Version 1.56 published on CPAN. Credits ------- Steffen Ullrich, reporter
