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

> Attackers can cause a denial of service in Perl applications using Net::DNS by sending crafted DNS packets with deep compression pointer chains.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 20 Jul 2026
- **Updated:** 30 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-64194, GHSA-m3gj-74x3-vc94, SUSE-SU-2026:3431-1, SUSE-SU-2026:3456-1, UBUNTU-CVE-2026-64194

## What is CVE-2026-64194?

CVE-2026-64194 is a high-severity denial of service vulnerability in NLNETLABS Net::DNS, published on 20 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-674 (Uncontrolled Recursion)

## Which versions are affected by CVE-2026-64194?


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `perl-Net-DNS` | SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOS | All versions | 1.14-150000.3.3.1 |
| `perl-Net-DNS` | SUSE:Linux Enterprise High Performance Computing 15 SP4-LTSS | All versions | 1.14-150000.3.3.1 |
| `perl-Net-DNS` | SUSE:Linux Enterprise High Performance Computing 15 SP5-ESPOS | All versions | 1.14-150000.3.3.1 |
| `perl-Net-DNS` | SUSE:Linux Enterprise High Performance Computing 15 SP5-LTSS | All versions | 1.14-150000.3.3.1 |
| `perl-Net-DNS` | SUSE:Linux Enterprise Module for Basesystem 15 SP7 | All versions | 1.14-150000.3.3.1 |
| `perl-Net-DNS` | SUSE:Linux Enterprise Server 12 SP5-LTSS | All versions | 0.73-5.3.1 |
| `perl-Net-DNS` | SUSE:Linux Enterprise Server 15 SP4-LTSS | All versions | 1.14-150000.3.3.1 |
| `perl-Net-DNS` | SUSE:Linux Enterprise Server 15 SP5-LTSS | All versions | 1.14-150000.3.3.1 |
| `perl-Net-DNS` | SUSE:Linux Enterprise Server 15 SP6-LTSS | All versions | 1.14-150000.3.3.1 |
| `perl-Net-DNS` | SUSE:Linux Enterprise Server LTSS Extended Security 12 SP5 | All versions | 0.73-5.3.1 |
| `perl-Net-DNS` | SUSE:Linux Enterprise Server for SAP Applications 15 SP4 | All versions | 1.14-150000.3.3.1 |
| `perl-Net-DNS` | SUSE:Linux Enterprise Server for SAP Applications 15 SP5 | All versions | 1.14-150000.3.3.1 |
| `perl-Net-DNS` | SUSE:Linux Enterprise Server for SAP Applications 15 SP6 | All versions | 1.14-150000.3.3.1 |

## How do I fix CVE-2026-64194?

Upgrade to a fixed version.

## Is CVE-2026-64194 being exploited?

There is no known exploitation of CVE-2026-64194 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-64194 and fix it if it is affected.

What it is: CVE-2026-64194 is a high-severity denial of service vulnerability in NLNETLABS Net::DNS, published on 20 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-64194 in the wild and no public exploit code.

Affected product: NLNETLABS Net::DNS. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-64194/ (Markdown: https://insights.sbomify.com/CVE-2026-64194/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-64194
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-64194
- OSV: https://osv.dev/vulnerability/CVE-2026-64194

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-64194/
Summaries are generated and may contain mistakes; the official description above is the record.