RHSA-2026:40574

Vulnerability from csaf_redhat - Published: 2026-07-16 01:07 - Updated: 2026-10-30 07:44
Summary
Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update
Severity
Important
Notes
Topic: An update for Red Hat Hardened Images RPMs is now available.
Details: This update includes the following RPMs: c-ares: * c-ares-1.34.8-2.hum1 (aarch64, x86_64) * c-ares-devel-1.34.8-2.hum1 (aarch64, x86_64) * c-ares-1.34.8-2.hum1.src (src)
Terms of Use: This content is licensed under the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/). If you distribute this content, or a modified version of it, you must provide attribution to Red Hat Inc. and provide a link to the original.
CVE-2026-69184

A flaw was found in c-ares, an asynchronous resolver library. The 'ares_dns_name_parse()' function does not properly limit the total pointer hops or assembled name length when enforcing backward DNS compression pointers. A remote attacker, operating a malicious DNS server, can send a specially crafted DNS response containing a long descending pointer chain. This can lead to excessive CPU consumption, causing the single-threaded c-ares event loop to stall and resulting in a denial of service for DNS resolution.

7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE-770 - Allocation of Resources Without Limits or Throttling
Affected products
Product Identifier Version Remediation
Unresolved product id: Red Hat Hardened Images:c-ares-0:1.34.8-2.hum1@aarch64 —
Vendor Fix fix
Workaround
Unresolved product id: Red Hat Hardened Images:c-ares-0:1.34.8-2.hum1@src —
Vendor Fix fix
Workaround
Unresolved product id: Red Hat Hardened Images:c-ares-0:1.34.8-2.hum1@x86_64 —
Vendor Fix fix
Workaround
Unresolved product id: Red Hat Hardened Images:c-ares-devel-0:1.34.8-2.hum1@aarch64 —
Vendor Fix fix
Workaround
Unresolved product id: Red Hat Hardened Images:c-ares-devel-0:1.34.8-2.hum1@x86_64 —
Vendor Fix fix
Workaround
Threats
Impact Important
CVE-2026-69186

A flaw was found in c-ares, an asynchronous resolver library. A remote attacker can send a specially crafted DNS response that causes the `ares_dns_parse()` function to trust attacker-controlled record counts without validating if the response contains enough bytes for the claimed records. This can lead to disproportionate heap memory reservation, resulting in a memory-amplification denial of service (DoS) by degrading or denying name resolution.

7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE-1284 - Improper Validation of Specified Quantity in Input
Affected products
Fixed 5 products, the same list as for CVE-2026-69184
Threats
Impact Important
References
To clipboard 

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        "name": "Allocation of Resources Without Limits or Throttling"
      },
      "discovery_date": "2026-09-22T18:25:12.267354+00:00",
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          "text": "2538396"
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        {
          "category": "description",
          "text": "A flaw was found in c-ares, an asynchronous resolver library. The \u0027ares_dns_name_parse()\u0027 function does not properly limit the total pointer hops or assembled name length when enforcing backward DNS compression pointers. A remote attacker, operating a malicious DNS server, can send a specially crafted DNS response containing a long descending pointer chain. This can lead to excessive CPU consumption, causing the single-threaded c-ares event loop to stall and resulting in a denial of service for DNS resolution.",
          "title": "Vulnerability description"
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        {
          "category": "summary",
          "text": "c-ares: c-ares: CPU exhaustion denial of service via unbounded DNS name compression pointer chains",
          "title": "Vulnerability summary"
        },
        {
          "category": "other",
          "text": "A flaw was found in the c-ares asynchronous DNS resolver library. Red Hat rates this flaw as Important. A remote attacker who can supply DNS responses to an application using a vulnerable c-ares build can send a crafted DNS message containing a long compression-pointer chain that causes quadratic name-decompression work in ares_dns_name_parse(). Because c-ares uses a single-threaded event loop, a single crafted response can stall DNS resolution for the process. Impact is limited to availability; the flaw does not cause memory corruption or information disclosure. The vulnerable DNS name parser is present in c-ares 1.21 and later through 1.34.6 and is fixed in 1.34.7. Red Hat Enterprise Linux 10 ships c-ares 1.25.0 or 1.34.6 and is affected. Red Hat Enterprise Linux 6, 7, 8, and 9 ship older c-ares versions (1.10.x through 1.19.x) that do not include this parser and are not affected. Red Hat\u0027s CVSS v3.1 score is 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H), matching the upstream High rating, because one crafted response is sufficient to deny name resolution.",
          "title": "Statement"
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        }
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          "Red Hat Hardened Images:c-ares-0:1.34.8-2.hum1@x86_64",
          "Red Hat Hardened Images:c-ares-devel-0:1.34.8-2.hum1@aarch64",
          "Red Hat Hardened Images:c-ares-devel-0:1.34.8-2.hum1@x86_64"
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          "summary": "Canonical URL",
          "url": "https://access.redhat.com/security/cve/CVE-2026-69184"
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          "summary": "RHBZ#2538396",
          "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2538396"
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          "summary": "https://www.cve.org/CVERecord?id=CVE-2026-69184",
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        {
          "category": "external",
          "summary": "https://nvd.nist.gov/vuln/detail/CVE-2026-69184",
          "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-69184"
        },
        {
          "category": "external",
          "summary": "https://github.com/c-ares/c-ares/commit/5c8341ba6ff3a8e4e4dfd616f8ed0418838b8b7b",
          "url": "https://github.com/c-ares/c-ares/commit/5c8341ba6ff3a8e4e4dfd616f8ed0418838b8b7b"
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        {
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        {
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          "summary": "https://github.com/c-ares/c-ares/pull/1164",
          "url": "https://github.com/c-ares/c-ares/pull/1164"
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          "summary": "https://github.com/c-ares/c-ares/pull/1210",
          "url": "https://github.com/c-ares/c-ares/pull/1210"
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        {
          "category": "external",
          "summary": "https://github.com/c-ares/c-ares/releases/tag/v1.34.7",
          "url": "https://github.com/c-ares/c-ares/releases/tag/v1.34.7"
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        {
          "category": "external",
          "summary": "https://github.com/c-ares/c-ares/security/advisories/GHSA-pjmc-gx33-gc76",
          "url": "https://github.com/c-ares/c-ares/security/advisories/GHSA-pjmc-gx33-gc76"
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      ],
      "release_date": "2026-09-18T17:26:52.210000+00:00",
      "remediations": [
        {
          "category": "vendor_fix",
          "date": "2026-07-16T01:07:51+00:00",
          "details": "For details on how to apply this update, which includes the changes described in this advisory, refer to:\nhttps://images.redhat.com/",
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            "Red Hat Hardened Images:c-ares-0:1.34.8-2.hum1@src",
            "Red Hat Hardened Images:c-ares-0:1.34.8-2.hum1@x86_64",
            "Red Hat Hardened Images:c-ares-devel-0:1.34.8-2.hum1@aarch64",
            "Red Hat Hardened Images:c-ares-devel-0:1.34.8-2.hum1@x86_64"
          ],
          "restart_required": {
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          },
          "url": "https://access.redhat.com/errata/RHSA-2026:40574"
        },
        {
          "category": "workaround",
          "details": "Configure applications that use c-ares to query only trusted DNS resolvers over a trusted network path. Restrict DNS responses from untrusted sources so a malicious or on-path resolver cannot deliver crafted replies.",
          "product_ids": [
            "Red Hat Hardened Images:c-ares-0:1.34.8-2.hum1@aarch64",
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            "Red Hat Hardened Images:c-ares-devel-0:1.34.8-2.hum1@aarch64",
            "Red Hat Hardened Images:c-ares-devel-0:1.34.8-2.hum1@x86_64"
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      ],
      "scores": [
        {
          "cvss_v3": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "products": [
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            "Red Hat Hardened Images:c-ares-0:1.34.8-2.hum1@src",
            "Red Hat Hardened Images:c-ares-0:1.34.8-2.hum1@x86_64",
            "Red Hat Hardened Images:c-ares-devel-0:1.34.8-2.hum1@aarch64",
            "Red Hat Hardened Images:c-ares-devel-0:1.34.8-2.hum1@x86_64"
          ]
        }
      ],
      "threats": [
        {
          "category": "impact",
          "details": "Important"
        }
      ],
      "title": "c-ares: c-ares: CPU exhaustion denial of service via unbounded DNS name compression pointer chains"
    },
    {
      "cve": "CVE-2026-69186",
      "cwe": {
        "id": "CWE-1284",
        "name": "Improper Validation of Specified Quantity in Input"
      },
      "discovery_date": "2026-09-22T17:25:55.228819+00:00",
      "ids": [
        {
          "system_name": "Red Hat Bugzilla ID",
          "text": "2538212"
        }
      ],
      "notes": [
        {
          "category": "description",
          "text": "A flaw was found in c-ares, an asynchronous resolver library. A remote attacker can send a specially crafted DNS response that causes the `ares_dns_parse()` function to trust attacker-controlled record counts without validating if the response contains enough bytes for the claimed records. This can lead to disproportionate heap memory reservation, resulting in a memory-amplification denial of service (DoS) by degrading or denying name resolution.",
          "title": "Vulnerability description"
        },
        {
          "category": "summary",
          "text": "c-ares: c-ares: Denial of Service via unvalidated DNS header record counts",
          "title": "Vulnerability summary"
        },
        {
          "category": "other",
          "text": "A flaw was found in the c-ares asynchronous DNS resolver library. Red Hat rates this flaw as Important. A remote attacker who can supply DNS responses to an application using a vulnerable c-ares build can send a crafted DNS message in which attacker-controlled ANCOUNT, NSCOUNT, and ARCOUNT header fields are trusted by ares_dns_parse() before the library verifies that the response contains enough bytes for the claimed records. Because parsing runs before transaction ID and question validation, a very small message can trigger pre-allocation of disproportionately large resource-record arrays on the heap, and repeated malicious responses can drive large allocation and release cycles that degrade or deny name resolution. Impact is limited to availability; the flaw does not cause memory corruption or information disclosure. The vulnerable pre-allocation path was introduced with the modern DNS record parser (c-ares 1.21 and later) and is fixed in 1.34.7. Red Hat Enterprise Linux 10 ships c-ares 1.25.0 or 1.34.6 and is affected. Red Hat Enterprise Linux 6, 7, 8, and 9 ship older c-ares versions that do not include this parser and are not affected. Red Hat\u0027s severity of Important (CVSS 7.5, AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) is higher than the upstream Moderate rating (CVSS 5.3, A:L) because Red Hat assesses the availability impact of sustained malicious DNS responses on name resolution as high.",
          "title": "Statement"
        },
        {
          "category": "general",
          "text": "The CVSS score(s) listed for this vulnerability do not reflect the associated product\u0027s status, and are included for informational purposes to better understand the severity of this vulnerability.",
          "title": "CVSS score applicability"
        }
      ],
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          "Red Hat Hardened Images:c-ares-0:1.34.8-2.hum1@x86_64",
          "Red Hat Hardened Images:c-ares-devel-0:1.34.8-2.hum1@aarch64",
          "Red Hat Hardened Images:c-ares-devel-0:1.34.8-2.hum1@x86_64"
        ]
      },
      "references": [
        {
          "category": "self",
          "summary": "Canonical URL",
          "url": "https://access.redhat.com/security/cve/CVE-2026-69186"
        },
        {
          "category": "external",
          "summary": "RHBZ#2538212",
          "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2538212"
        },
        {
          "category": "external",
          "summary": "https://www.cve.org/CVERecord?id=CVE-2026-69186",
          "url": "https://www.cve.org/CVERecord?id=CVE-2026-69186"
        },
        {
          "category": "external",
          "summary": "https://nvd.nist.gov/vuln/detail/CVE-2026-69186",
          "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-69186"
        },
        {
          "category": "external",
          "summary": "https://github.com/c-ares/c-ares/commit/e47c203f91cd8b749c8736bc18d75a31ffdec8f4",
          "url": "https://github.com/c-ares/c-ares/commit/e47c203f91cd8b749c8736bc18d75a31ffdec8f4"
        },
        {
          "category": "external",
          "summary": "https://github.com/c-ares/c-ares/commit/eaded4cb200b2a5f8d73f11021ff7c8d6968aaab",
          "url": "https://github.com/c-ares/c-ares/commit/eaded4cb200b2a5f8d73f11021ff7c8d6968aaab"
        },
        {
          "category": "external",
          "summary": "https://github.com/c-ares/c-ares/pull/1134",
          "url": "https://github.com/c-ares/c-ares/pull/1134"
        },
        {
          "category": "external",
          "summary": "https://github.com/c-ares/c-ares/releases/tag/v1.34.7",
          "url": "https://github.com/c-ares/c-ares/releases/tag/v1.34.7"
        },
        {
          "category": "external",
          "summary": "https://github.com/c-ares/c-ares/security/advisories/GHSA-jv8r-gqr9-68wj",
          "url": "https://github.com/c-ares/c-ares/security/advisories/GHSA-jv8r-gqr9-68wj"
        }
      ],
      "release_date": "2026-09-18T17:25:42.440000+00:00",
      "remediations": [
        {
          "category": "vendor_fix",
          "date": "2026-07-16T01:07:51+00:00",
          "details": "For details on how to apply this update, which includes the changes described in this advisory, refer to:\nhttps://images.redhat.com/",
          "product_ids": [
            "Red Hat Hardened Images:c-ares-0:1.34.8-2.hum1@aarch64",
            "Red Hat Hardened Images:c-ares-0:1.34.8-2.hum1@src",
            "Red Hat Hardened Images:c-ares-0:1.34.8-2.hum1@x86_64",
            "Red Hat Hardened Images:c-ares-devel-0:1.34.8-2.hum1@aarch64",
            "Red Hat Hardened Images:c-ares-devel-0:1.34.8-2.hum1@x86_64"
          ],
          "restart_required": {
            "category": "none"
          },
          "url": "https://access.redhat.com/errata/RHSA-2026:40574"
        },
        {
          "category": "workaround",
          "details": "Configure applications that use c-ares to query only trusted DNS resolvers over a trusted network path (CME-202 host firewall; CME-203 network segmentation). Restrict DNS responses from untrusted sources so a malicious or on-path resolver cannot deliver crafted replies. There is no complete library-level workaround; apply a fixed c-ares update when available.",
          "product_ids": [
            "Red Hat Hardened Images:c-ares-0:1.34.8-2.hum1@aarch64",
            "Red Hat Hardened Images:c-ares-0:1.34.8-2.hum1@src",
            "Red Hat Hardened Images:c-ares-0:1.34.8-2.hum1@x86_64",
            "Red Hat Hardened Images:c-ares-devel-0:1.34.8-2.hum1@aarch64",
            "Red Hat Hardened Images:c-ares-devel-0:1.34.8-2.hum1@x86_64"
          ]
        }
      ],
      "scores": [
        {
          "cvss_v3": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "products": [
            "Red Hat Hardened Images:c-ares-0:1.34.8-2.hum1@aarch64",
            "Red Hat Hardened Images:c-ares-0:1.34.8-2.hum1@src",
            "Red Hat Hardened Images:c-ares-0:1.34.8-2.hum1@x86_64",
            "Red Hat Hardened Images:c-ares-devel-0:1.34.8-2.hum1@aarch64",
            "Red Hat Hardened Images:c-ares-devel-0:1.34.8-2.hum1@x86_64"
          ]
        }
      ],
      "threats": [
        {
          "category": "impact",
          "details": "Important"
        }
      ],
      "title": "c-ares: c-ares: Denial of Service via unvalidated DNS header record counts"
    }
  ]
}



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