UBUNTU-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.

References

Affected packages

Ubuntu:24.04:LTS / c-ares

Package

Name: c-ares
Purl: pkg:deb/ubuntu/c-ares?arch=source&distro=noble

Affected ranges

Type: ECOSYSTEM
Events: Introduced

0 Unknown introduced version / All previous versions are affected

Fixed

1.27.0-1.0ubuntu1.1

Affected versions

1.*

1.19.1-3

1.20.1-1

1.26.0-1

1.27.0-1

1.27.0-1.0ubuntu1

Ecosystem specific

{
    "availability":  "No subscription required",
    "binaries":  [
        {
            "binary_name":  "libcares2",
            "binary_version":  "1.27.0-1.0ubuntu1.1"
        }
    ]
}

Database specific

source

"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-69186.json"

Ubuntu:26.04:LTS / c-ares

Package

Name: c-ares
Purl: pkg:deb/ubuntu/c-ares?arch=source&distro=resolute

Affected ranges

Type: ECOSYSTEM
Events: Introduced

0 Unknown introduced version / All previous versions are affected

Fixed

1.34.6-1ubuntu0.2

Affected versions

1.*

1.34.5-1

1.34.6-1

1.34.6-1ubuntu0.1

Ecosystem specific

{
    "availability":  "No subscription required",
    "binaries":  [
        {
            "binary_name":  "libc-ares2",
            "binary_version":  "1.34.6-1ubuntu0.2"
        },
        {
            "binary_name":  "libcares2",
            "binary_version":  "1.34.6-1ubuntu0.2"
        }
    ]
}

Database specific

source

"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-69186.json"