Resource exhaustion in C-Ares
CVE-2026-69186
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.
Vulnerability class: DoS (Denial of Service)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.
EPSS exploit prediction
EPSS: 0.005 (40.4th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 40th percentile — 40.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.005 · newest: 0.005 · change: -0.001
Affected products
- C-Ares — versions < 1.34.7
Weakness classification (CWE)
References
Frequently asked questions
- What is CVE-2026-69186?
- CVE-2026-69186 is a medium-severity vulnerability in C-Ares, classified under Uncontrolled Resource Consumption. CVSS score: 5.3/10. Published 2026-09-18.
- How severe is CVE-2026-69186?
- Medium severity. CVSS v3 base score is 5.3 out of 10.