{ "document": { "aggregate_severity": { "text": "Medium" }, "category": "csaf_vex", "csaf_version": "2.0", "distribution": { "text": "TuxCare License Agreement", "tlp": { "label": "WHITE", "url": "https://www.first.org/tlp/" } }, "lang": "en", "notes": [ { "category": "legal_disclaimer", "text": "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 Cloud Linux Inc. and provide a link to the original.", "title": "Terms of Use" } ], "publisher": { "category": "vendor", "contact_details": "https://tuxcare.com/contact/", "name": "TuxCare", "namespace": "https://tuxcare.com/" }, "references": [ { "category": "self", "summary": "Canonical URL", "url": "https://security.tuxcare.com/csaf/v2/els_os/oraclelinux6els/vex/2026/cve-2026-42923-els_os-oraclelinux6els.json" } ], "tracking": { "current_release_date": "2026-10-28T11:32:51Z", "generator": { "date": "2026-10-28T11:32:51Z", "engine": { "name": "pyCSAF" } }, "id": "CVE-2026-42923-ELS_OS-ORACLELINUX6ELS", "initial_release_date": "2026-05-20T10:16:00Z", "revision_history": [ { "date": "2026-05-20T10:16:00Z", "number": "1", "summary": "Initial version" }, { "date": "2026-10-28T11:32:51Z", "number": "2", "summary": "Official Publication" } ], "status": "final", "version": "2" }, "title": "Security 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"vulnerabilities": [ { "cve": "CVE-2026-42923", "cwe": { "id": "CWE-407", "name": "Inefficient Algorithmic Complexity" }, "notes": [ { "category": "description", "text": "NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the DNSSEC validator where the code path to consult the negative cache for DS records does not take into account the limit on NSEC3 hash calculations introduced in 1.19.1. This leads to degradation of service during the attack. An adversary that controls a DNSSEC signed zone can exploit this by signing NSEC3 records with acceptably high iterations for child delegations and querying a vulnerable Unbound. Unbound will keep performing the allowed hash calculations on the NSEC3 records and will not limit the work by the mitigation introduced in 1.19.1. As a side effect, a global lock for the negative cache will be held for the duration of the hashing, blocking other threads that need to consult the negative cache. Coordinated attacks could raise the vulnerability to denial of service. Unbound 1.25.1 contains a patch with a fix to bound the vulnerable code path with the existing limit for NSEC3 hash calculations.", "title": "Vulnerability description" }, { "category": "general", "text": "The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.", "title": "CVSS score applicability" } ], "product_status": { "known_affected": [ "Oracle-Linux-6:unbound-0:1.4.20-29.el6_10.1.i686", "Oracle-Linux-6:unbound-0:1.4.20-29.el6_10.1.tuxcare.els2.i686", "Oracle-Linux-6:unbound-0:1.4.20-29.el6_10.1.tuxcare.els2.x86_64", "Oracle-Linux-6:unbound-0:1.4.20-29.el6_10.1.x86_64", "Oracle-Linux-6:unbound-devel-0:1.4.20-29.el6_10.1.i686", "Oracle-Linux-6:unbound-devel-0:1.4.20-29.el6_10.1.tuxcare.els2.i686", "Oracle-Linux-6:unbound-devel-0:1.4.20-29.el6_10.1.tuxcare.els2.x86_64", "Oracle-Linux-6:unbound-devel-0:1.4.20-29.el6_10.1.x86_64", "Oracle-Linux-6:unbound-libs-0:1.4.20-29.el6_10.1.i686", "Oracle-Linux-6:unbound-libs-0:1.4.20-29.el6_10.1.tuxcare.els2.i686", "Oracle-Linux-6:unbound-libs-0:1.4.20-29.el6_10.1.tuxcare.els2.x86_64", "Oracle-Linux-6:unbound-libs-0:1.4.20-29.el6_10.1.x86_64", "Oracle-Linux-6:unbound-python-0:1.4.20-29.el6_10.1.i686", "Oracle-Linux-6:unbound-python-0:1.4.20-29.el6_10.1.tuxcare.els2.i686", "Oracle-Linux-6:unbound-python-0:1.4.20-29.el6_10.1.tuxcare.els2.x86_64", "Oracle-Linux-6:unbound-python-0:1.4.20-29.el6_10.1.x86_64" ] }, "references": [ { "category": "self", "summary": "Canonical URL", "url": "https://cve.tuxcare.com/els/cve/CVE-2026-42923" }, { "category": "external", "summary": "https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-42923.txt", "url": "https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-42923.txt" } ], "release_date": "2026-05-20T10:16:00Z", "remediations": [ { "category": "no_fix_planned", "date": "2026-10-15T10:08:31.533564Z", "details": "Impact is limited to resolver availability: the flaw causes excessive NSEC3 hashing when consulting the DS negative cache, briefly holding a cache lock and slowing/stalling lookups, with no confidentiality or integrity effect. Exploitation requires an attacker who controls a DNSSEC‑signed zone and can induce queries to it, and the impact is confined to the Unbound recursive resolver process rather than other services or hosts. Given these preconditions and the DoS‑only outcome, systems running Unbound can reasonably deprioritize this issue in enterprise VM/server environments.", "product_ids": [ "Oracle-Linux-6:unbound-0:1.4.20-29.el6_10.1.i686", "Oracle-Linux-6:unbound-0:1.4.20-29.el6_10.1.tuxcare.els2.i686", "Oracle-Linux-6:unbound-0:1.4.20-29.el6_10.1.tuxcare.els2.x86_64", "Oracle-Linux-6:unbound-0:1.4.20-29.el6_10.1.x86_64", "Oracle-Linux-6:unbound-devel-0:1.4.20-29.el6_10.1.i686", "Oracle-Linux-6:unbound-devel-0:1.4.20-29.el6_10.1.tuxcare.els2.i686", "Oracle-Linux-6:unbound-devel-0:1.4.20-29.el6_10.1.tuxcare.els2.x86_64", "Oracle-Linux-6:unbound-devel-0:1.4.20-29.el6_10.1.x86_64", "Oracle-Linux-6:unbound-libs-0:1.4.20-29.el6_10.1.i686", "Oracle-Linux-6:unbound-libs-0:1.4.20-29.el6_10.1.tuxcare.els2.i686", "Oracle-Linux-6:unbound-libs-0:1.4.20-29.el6_10.1.tuxcare.els2.x86_64", "Oracle-Linux-6:unbound-libs-0:1.4.20-29.el6_10.1.x86_64", "Oracle-Linux-6:unbound-python-0:1.4.20-29.el6_10.1.i686", "Oracle-Linux-6:unbound-python-0:1.4.20-29.el6_10.1.tuxcare.els2.i686", "Oracle-Linux-6:unbound-python-0:1.4.20-29.el6_10.1.tuxcare.els2.x86_64", "Oracle-Linux-6:unbound-python-0:1.4.20-29.el6_10.1.x86_64" ] } ], "scores": [ { "cvss_v3": { "attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "LOW", "baseScore": 5.3, "baseSeverity": "MEDIUM", "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:L", "version": "3.1" }, "products": [ "Oracle-Linux-6:unbound-0:1.4.20-29.el6_10.1.i686", "Oracle-Linux-6:unbound-0:1.4.20-29.el6_10.1.tuxcare.els2.i686", "Oracle-Linux-6:unbound-0:1.4.20-29.el6_10.1.tuxcare.els2.x86_64", "Oracle-Linux-6:unbound-0:1.4.20-29.el6_10.1.x86_64", "Oracle-Linux-6:unbound-devel-0:1.4.20-29.el6_10.1.i686", "Oracle-Linux-6:unbound-devel-0:1.4.20-29.el6_10.1.tuxcare.els2.i686", "Oracle-Linux-6:unbound-devel-0:1.4.20-29.el6_10.1.tuxcare.els2.x86_64", "Oracle-Linux-6:unbound-devel-0:1.4.20-29.el6_10.1.x86_64", "Oracle-Linux-6:unbound-libs-0:1.4.20-29.el6_10.1.i686", "Oracle-Linux-6:unbound-libs-0:1.4.20-29.el6_10.1.tuxcare.els2.i686", "Oracle-Linux-6:unbound-libs-0:1.4.20-29.el6_10.1.tuxcare.els2.x86_64", "Oracle-Linux-6:unbound-libs-0:1.4.20-29.el6_10.1.x86_64", "Oracle-Linux-6:unbound-python-0:1.4.20-29.el6_10.1.i686", "Oracle-Linux-6:unbound-python-0:1.4.20-29.el6_10.1.tuxcare.els2.i686", "Oracle-Linux-6:unbound-python-0:1.4.20-29.el6_10.1.tuxcare.els2.x86_64", "Oracle-Linux-6:unbound-python-0:1.4.20-29.el6_10.1.x86_64" ] } ], "threats": [ { "category": "impact", "details": "Moderate" } ] } ] }