c-ares up to 1.34.6 DNS Parsing ares_dns_parse allocation of resources

Summaryinfo

A vulnerability was found in c-ares up to 1.34.6. It has been rated as problematic. Impacted is the function ares_dns_parse of the component DNS Parsing. The manipulation leads to allocation of resources. This vulnerability is uniquely identified as CVE-2026-69186. The attack is possible to be carried out remotely. No exploit exists. Upgrading the affected component is advised.

Detailsinfo

A vulnerability was found in c-ares up to 1.34.6 and classified as problematic. This issue affects the function ares_dns_parse of the component DNS Parsing. The manipulation with an unknown input leads to a allocation of resources vulnerability. Using CWE to declare the problem leads to CWE-770. The product allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor. Impacted is availability. The summary by CVE is:

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.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-69186 since 08/03/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1499 according to MITRE ATT&CK.

Upgrading to version 1.34.7 eliminates this vulnerability.

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Productinfo

Name

• c-ares

Version

• 1.34.0
• 1.34.1
• 1.34.2
• 1.34.3
• 1.34.4
• 1.34.5
• 1.34.6

Website

• Product: https://github.com/c-ares/c-ares/

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