# CVE-2026-69186: c-ares: Memory-amplification denial of service via unvalidated DNS header record counts

> A malicious DNS response can trigger excessive memory allocation in c-ares, leading to denial of service for applications using the library.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 18 Sep 2026
- **Updated:** 18 Sep 2026
- **Also known as:** AZL-103304, AZL-103454, BELL-CVE-2026-69186, DEBIAN-CVE-2026-69186, ECHO-9e60-294a-7216, GHSA-jv8r-gqr9-68wj, MINI-vfrm-8j62-rm2w, UBUNTU-CVE-2026-69186

## What is CVE-2026-69186?

CVE-2026-69186 is a medium-severity denial of service vulnerability in c-ares, published on 18 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

c-ares is an asynchronous resolver library. Prior to 1.34.7, ares_dns_parse() trusts the attacker-controlled ANCOUNT, NSCOUNT, and ARCOUNT fields before confirming that the DNS response contains enough bytes for the claimed records. Because process_answer() invokes parsing before transaction ID and question validation, a malicious DNS response can cause ares_dns_record_rr_prealloc() and ares_array_set_size() to reserve disproportionate heap memory for a tiny message. Repeated responses create large allocation and release cycles that can degrade or deny name resolution, without causing memory corruption or information disclosure. This issue is fixed in version 1.34.7.

Weakness: CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2026-69186?


## How do I fix CVE-2026-69186?

Upgrade to a fixed version.

## Is CVE-2026-69186 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-69186 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-69186 and fix it if it is affected.

What it is: CVE-2026-69186 is a medium-severity denial of service vulnerability in c-ares, published on 18 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-69186 exists.

Affected product: c-ares. 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-2026-69186/ (Markdown: https://insights.sbomify.com/CVE-2026-69186/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-69186
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-69186
- OSV: https://osv.dev/vulnerability/CVE-2026-69186

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-69186/
Summaries are generated and may contain mistakes; the official description above is the record.