# CVE-2026-64194: libnet-dns-perl: Net::DNS versions through 1.55 for Perl allow Denial of Service via deep DNS compression pointer chains

CVE-2026-64194 is fixed in 4 products on 1 platform, first by DEBIAN-CVE-2026-64194, released July 24, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-64194
- Priority: High
- CVSS: 7.5 (high)
- EPSS: 0.0068
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jul 20, 2026

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | libnet-dns-perl Debian 12.15 (bookworm) | 1.36-1+deb12u1 | [DEBIAN-CVE-2026-64194](https://patchblox.com/security/data/fix/linux/debian-cve-2026-64194.md) | Jul 24, 2026 |
| Linux | libnet-dns-perl Debian 13.5 (trixie) | 1.56-0+deb13u1 | [DEBIAN-CVE-2026-64194](https://patchblox.com/security/data/fix/linux/debian-cve-2026-64194.md) | Jul 24, 2026 |
| Linux | libnet-dns-perl Debian 14 | 1.56-1 | [DEBIAN-CVE-2026-64194](https://patchblox.com/security/data/fix/linux/debian-cve-2026-64194.md) | Jul 24, 2026 |
| Linux | perl-Net-DNS amzn 2023 | 1.56-1.amzn2023.0.1 | [ALAS2023-2026-2046](https://patchblox.com/security/data/fix/linux/alas2023-2026-2046.md) | Aug 3, 2026 |
| Linux | perl-Net-DNS opensuse-leap 16.0 | 1.570.0-bp160.1.1 | [OPENSUSE-SU-2026:21859-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21859-1.md) | Sep 15, 2026 |
| Linux | perl-Net-DNS sles 15.6 | 1.14-150000.3.3.1 | [SUSE-SU-2026:3456-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-3456-1.md) | Aug 3, 2026 |
| Linux | perl-Net-DNS sles 15.7 | 1.14-150000.3.3.1 | [SUSE-SU-2026:3456-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-3456-1.md) | Aug 3, 2026 |
| Linux | perl-Net-DNS-Nameserver amzn 2023 | 1.56-1.amzn2023.0.1 | [ALAS2023-2026-2046](https://patchblox.com/security/data/fix/linux/alas2023-2026-2046.md) | Aug 3, 2026 |
| Linux | perl-Net-DNS-tests amzn 2023 | 1.56-1.amzn2023.0.1 | [ALAS2023-2026-2046](https://patchblox.com/security/data/fix/linux/alas2023-2026-2046.md) | Aug 3, 2026 |

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Data as of 2026-11-09T01:18:40Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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