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Fencer Vulns
medium 5.3

CVE-2026-69186 json

c-ares: Memory-amplification denial of service via unvalidated DNS header record counts

published 2026-09-18 51 d ago modified 2026-09-23 46 d ago also EUVD-2026-83212

cvss
5.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 40%
public exploits
0
none known

Summary

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.

Patch / fix

  • c-ares Debian 14 1.34.7-1

debian advisories DEBIAN-CVE-2026-69186

  • c-ares Ubuntu 24.04 LTS 1.27.0-1.0ubuntu1.1
  • c-ares Ubuntu 26.04 LTS 1.34.6-1ubuntu0.2

ubuntu advisories UBUNTU-CVE-2026-69186

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • c-ares hummingbird 1 1.34.8-2.hum1

red hat advisories RHSA-2026:40574

  • c-ares SLES for SAP 15 SP6, SLES for SAP 15 SP5, SLES for SAP 15 SP4 +11 more 1.34.8-150000.3.29.1
  • c-ares SLES for SAP applications 16.0, SLES 16.0 1.34.8-160000.1.1
  • c-ares Linux Micro 6.1 1.34.8-slfo.1.1_1.1
  • c-ares Linux Micro 6.0 1.34.8-1.1

suse advisories SUSE-SU-2026:4021-1SUSE-SU-2026:23597-1SUSE-SU-2026:23414-1SUSE-SU-2026:23364-1

  • c-ares openSUSE Leap 16.0 1.34.8-160000.1.1
  • c-ares openSUSE Tumbleweed 1.34.8-1.1

opensuse advisories openSUSE-SU-2026:21721-1openSUSE-SU-2026:11593-1

  • c-ares Azure Linux 3.0 1.34.8-1

azure linux advisories AZL-103304

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-69186 updated cvss 7.5

c-ares: c-ares: Denial of Service via unvalidated DNS header record counts

  • Red Hat Enterprise Linux 10 c-ares Red Hat OpenShift Container Platform 4 openshift/ose-rhel-coreos-8, openshift/ose-rhel-coreos-9 Red Hat OpenShift Container Platform 5 openshift/ose-rhel-coreos-9
    affected: workaround, no fix available
  • Red Hat OpenShift Service Mesh 3 istio-proxy, istio-proxy-selinux
    under investigation
  • Red Hat Hardened Images c-ares 1.34.8-2.hum1
    fixed: vendor fix RHSA-2026:40574
  • Red Hat Enterprise Linux 6 c-ares Red Hat Enterprise Linux 7 c-ares Red Hat Enterprise Linux 8 npm, c-ares, nodejs, nodejs-libs, nodejs-nodemon, nodejs-full-i18n, +2 more Red Hat Enterprise Linux 9 npm, c-ares, nodejs, nodejs-libs, nodejs-full-i18n Red Hat Enterprise Linux 10 nodejs22
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
51 d ago

Exploit prediction

0.47% chance of exploitation in the next 30 days, higher than 40% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/c-ares/c-ares/security/advisories/GHSA-jv8r-gqr9-68wj referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Affected products

  • c-ares c-ares

Classification

Weakness
  • CWE-400 Uncontrolled Resource Consumption

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.