{"containers": {"cna": {"affected": [{"product": "BIND9", "vendor": "ISC", "versions": [{"status": "affected", "version": "Stable Branch 9.16.19"}, {"status": "affected", "version": "Development Branch 9.17.16"}, {"status": "affected", "version": "Supported Preview Edition 9.16.19-S1"}]}], "datePublic": "2021-08-18T00:00:00", "descriptions": [{"lang": "en", "value": "In BIND 9.16.19, 9.17.16. Also, version 9.16.19-S1 of BIND Supported Preview Edition When a vulnerable version of named receives a query under the circumstances described above, the named process will terminate due to a failed assertion check. The vulnerability affects only BIND 9 releases 9.16.19, 9.17.16, and release 9.16.19-S1 of the BIND Supported Preview Edition."}], "exploits": [{"lang": "en", "value": "We are not aware of any active exploits, but the conditions triggering the crash can occur during normal operations"}], "metrics": [{"cvssV3_1": {"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"}}], "problemTypes": [{"descriptions": [{"description": "If named attempts to respond over UDP with a response that is larger than the current effective interface maximum transmission unit (MTU), and if response-rate limiting (RRL) is active, an assertion failure is triggered (resulting in termination of the named server process). There are two ways for named to exceed the interface MTU: Direct configuration in named.conf setting max-udp-size to a value larger than the interface's MTU, or Path MTU discovery (PMTUD) informing the IP stack that it should use a smaller MTU for the interface and destination than the default max-udp-size value of 1232. Some operating systems allow packets received via other protocols to affect PMTUD values for DNS over UDP. While RRL is not enabled by default for user-defined views or the built-in default INTERNET (IN) class view, \"_default\", the built-in default CHAOS (CH) class view, \"_bind\", does have RRL enabled. Note that while this defect can be triggered through misconfiguration or by deliberate exploitation, it can also arise during normal operating conditions, even with hardened PMTUD settings. Affects BIND 9.16.19, 9.17.16. Also, version 9.16.19-S1 of BIND Supported Preview Edition.", "lang": "en", "type": "text"}]}], "providerMetadata": {"dateUpdated": "2021-09-09T08:06:12", "orgId": "404fd4d2-a609-4245-b543-2c944a302a22", "shortName": "isc"}, "references": [{"tags": ["x_refsource_CONFIRM"], "url": "https://kb.isc.org/v1/docs/cve-2021-25218"}, {"name": "[oss-security] 20210818 ISC has disclosed a vulnerability in BIND (CVE-2021-25218)", "tags": ["mailing-list", "x_refsource_MLIST"], "url": "http://www.openwall.com/lists/oss-security/2021/08/18/3"}, {"name": "[oss-security] 20210820 August BIND maintenance releases contain a defect affecting servers using the map zone file format (was: A vulnerability in BIND (CVE-2021-25218) will be announced 18 August 2021)", "tags": ["mailing-list", "x_refsource_MLIST"], "url": "http://www.openwall.com/lists/oss-security/2021/08/20/2"}, {"name": "FEDORA-2021-fbb258debf", "tags": ["vendor-advisory", "x_refsource_FEDORA"], "url": "https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZPJCLGSR4BTGFLBLGIE5TEQP2SNJKGVL/"}, {"tags": ["x_refsource_CONFIRM"], "url": "https://security.netapp.com/advisory/ntap-20210909-0002/"}], "solutions": [{"lang": "en", "value": "Upgrade to the patched release most closely related to your current version of BIND:\n\n BIND 9.16.20\n BIND 9.17.17\n\nBIND Supported Preview Edition is a special feature preview branch of BIND provided to eligible ISC support customers.\n\n BIND 9.16.20-S1"}], "source": {"discovery": "USER"}, "title": "A too-strict assertion check could be triggered when responses in BIND 9.16.19 and 9.17.16 require UDP fragmentation if RRL is in use", "workarounds": [{"lang": "en", "value": "Disabling RRL in all views, including the built-in CHAOS class view \"_bind\", prevents the faulty assertion from being reached. This can be done by removing all existing rate-limit statements from named.conf, and defining a replacement for the default CHAOS view:\n\nview override_bind chaos {\n recursion no;\n notify no;\n allow-new-zones no;\n max-cache-size 2M;\n\n zone \"version.bind\" chaos {\n type primary;\n database \"_builtin version\";\n };\n zone \"hostname.bind\" chaos {\n type primary;\n database \"_builtin hostname\";\n };\n zone \"authors.bind\" chaos {\n type primary;\n database \"_builtin authors\";\n };\n zone \"id.server\" chaos {\n type primary;\n database \"_builtin id\";\n };\n};"}], "x_generator": {"engine": "Vulnogram 0.0.9"}, "x_legacyV4Record": {"CVE_data_meta": {"ASSIGNER": "security-officer@isc.org", "DATE_PUBLIC": "2021-08-18T17:45:20.000Z", "ID": "CVE-2021-25218", "STATE": "PUBLIC", "TITLE": "A too-strict assertion check could be triggered when responses in BIND 9.16.19 and 9.17.16 require UDP fragmentation if RRL is in use"}, "affects": {"vendor": {"vendor_data": [{"product": {"product_data": [{"product_name": "BIND9", "version": {"version_data": [{"version_affected": "=", "version_name": "Stable Branch", "version_value": "9.16.19"}, {"version_affected": "=", "version_name": "Development Branch", "version_value": "9.17.16"}, {"version_affected": "=", "version_name": "Supported Preview Edition", "version_value": "9.16.19-S1"}]}}]}, "vendor_name": "ISC"}]}}, "data_format": "MITRE", "data_type": "CVE", "data_version": "4.0", "description": {"description_data": [{"lang": "eng", "value": "In BIND 9.16.19, 9.17.16. Also, version 9.16.19-S1 of BIND Supported Preview Edition When a vulnerable version of named receives a query under the circumstances described above, the named process will terminate due to a failed assertion check. The vulnerability affects only BIND 9 releases 9.16.19, 9.17.16, and release 9.16.19-S1 of the BIND Supported Preview Edition."}]}, "exploit": [{"lang": "en", "value": "We are not aware of any active exploits, but the conditions triggering the crash can occur during normal operations"}], "generator": {"engine": "Vulnogram 0.0.9"}, "impact": {"cvss": {"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"}}, "problemtype": {"problemtype_data": [{"description": [{"lang": "eng", "value": "If named attempts to respond over UDP with a response that is larger than the current effective interface maximum transmission unit (MTU), and if response-rate limiting (RRL) is active, an assertion failure is triggered (resulting in termination of the named server process). There are two ways for named to exceed the interface MTU: Direct configuration in named.conf setting max-udp-size to a value larger than the interface's MTU, or Path MTU discovery (PMTUD) informing the IP stack that it should use a smaller MTU for the interface and destination than the default max-udp-size value of 1232. Some operating systems allow packets received via other protocols to affect PMTUD values for DNS over UDP. While RRL is not enabled by default for user-defined views or the built-in default INTERNET (IN) class view, \"_default\", the built-in default CHAOS (CH) class view, \"_bind\", does have RRL enabled. Note that while this defect can be triggered through misconfiguration or by deliberate exploitation, it can also arise during normal operating conditions, even with hardened PMTUD settings. Affects BIND 9.16.19, 9.17.16. Also, version 9.16.19-S1 of BIND Supported Preview Edition."}]}]}, "references": {"reference_data": [{"name": "https://kb.isc.org/v1/docs/cve-2021-25218", "refsource": "CONFIRM", "url": "https://kb.isc.org/v1/docs/cve-2021-25218"}, {"name": "[oss-security] 20210818 ISC has disclosed a vulnerability in BIND (CVE-2021-25218)", "refsource": "MLIST", "url": "http://www.openwall.com/lists/oss-security/2021/08/18/3"}, {"name": "[oss-security] 20210820 August BIND maintenance releases contain a defect affecting servers using the map zone file format (was: A vulnerability in BIND (CVE-2021-25218) will be announced 18 August 2021)", "refsource": "MLIST", "url": "http://www.openwall.com/lists/oss-security/2021/08/20/2"}, {"name": "FEDORA-2021-fbb258debf", "refsource": "FEDORA", "url": "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/ZPJCLGSR4BTGFLBLGIE5TEQP2SNJKGVL/"}, {"name": "https://security.netapp.com/advisory/ntap-20210909-0002/", "refsource": "CONFIRM", "url": "https://security.netapp.com/advisory/ntap-20210909-0002/"}]}, "solution": [{"lang": "en", "value": "Upgrade to the patched release most closely related to your current version of BIND:\n\n BIND 9.16.20\n BIND 9.17.17\n\nBIND Supported Preview Edition is a special feature preview branch of BIND provided to eligible ISC support customers.\n\n BIND 9.16.20-S1"}], "source": {"discovery": "USER"}, "work_around": [{"lang": "en", "value": "Disabling RRL in all views, including the built-in CHAOS class view \"_bind\", prevents the faulty assertion from being reached. This can be done by removing all existing rate-limit statements from named.conf, and defining a replacement for the default CHAOS view:\n\nview override_bind chaos {\n recursion no;\n notify no;\n allow-new-zones no;\n max-cache-size 2M;\n\n zone \"version.bind\" chaos {\n type primary;\n database \"_builtin version\";\n };\n zone \"hostname.bind\" chaos {\n type primary;\n database \"_builtin hostname\";\n };\n zone \"authors.bind\" chaos {\n type primary;\n database \"_builtin authors\";\n };\n zone \"id.server\" chaos {\n type primary;\n database \"_builtin id\";\n };\n};"}]}}, "adp": [{"providerMetadata": {"orgId": "af854a3a-2127-422b-91ae-364da2661108", "shortName": "CVE", "dateUpdated": "2024-08-03T19:56:11.055Z"}, "title": "CVE Program Container", "references": [{"tags": ["x_refsource_CONFIRM", "x_transferred"], "url": "https://kb.isc.org/v1/docs/cve-2021-25218"}, {"name": "[oss-security] 20210818 ISC has disclosed a vulnerability in BIND (CVE-2021-25218)", "tags": ["mailing-list", "x_refsource_MLIST", "x_transferred"], "url": "http://www.openwall.com/lists/oss-security/2021/08/18/3"}, {"name": "[oss-security] 20210820 August BIND maintenance releases contain a defect affecting servers using the map zone file format (was: A vulnerability in BIND (CVE-2021-25218) will be announced 18 August 2021)", "tags": ["mailing-list", "x_refsource_MLIST", "x_transferred"], "url": "http://www.openwall.com/lists/oss-security/2021/08/20/2"}, {"name": "FEDORA-2021-fbb258debf", "tags": ["vendor-advisory", "x_refsource_FEDORA", "x_transferred"], "url": "https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZPJCLGSR4BTGFLBLGIE5TEQP2SNJKGVL/"}, {"tags": ["x_refsource_CONFIRM", "x_transferred"], "url": "https://security.netapp.com/advisory/ntap-20210909-0002/"}]}]}, "cveMetadata": {"assignerOrgId": "404fd4d2-a609-4245-b543-2c944a302a22", "assignerShortName": "isc", "cveId": "CVE-2021-25218", "datePublished": "2021-08-18T18:20:11.962739Z", "dateReserved": "2021-01-15T00:00:00", "dateUpdated": "2024-09-17T03:07:43.591Z", "state": "PUBLISHED"}, "dataType": "CVE_RECORD", "dataVersion": "5.1"}

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{"configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:a:isc:bind:9.16.19:*:*:*:-:*:*:*", "matchCriteriaId": "257443A7-F602-4043-A9B3-FAE11008FE87", "vulnerable": true}, {"criteria": "cpe:2.3:a:isc:bind:9.17.16:*:*:*:-:*:*:*", "matchCriteriaId": "A72E883B-262D-4BF0-B09E-488AD1D3B4FF", "vulnerable": true}, {"criteria": "cpe:2.3:a:isc:bind:9.17.16:s1:*:*:supported_preview:*:*:*", "matchCriteriaId": "074CB7B7-FC62-4AAB-9155-F158C199231E", "vulnerable": true}], "negate": false, "operator": "OR"}]}, {"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*", "matchCriteriaId": "A930E247-0B43-43CB-98FF-6CE7B8189835", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "In BIND 9.16.19, 9.17.16. Also, version 9.16.19-S1 of BIND Supported Preview Edition When a vulnerable version of named receives a query under the circumstances described above, the named process will terminate due to a failed assertion check. The vulnerability affects only BIND 9 releases 9.16.19, 9.17.16, and release 9.16.19-S1 of the BIND Supported Preview Edition."}, {"lang": "es", "value": "En BIND versiones 9.16.19, 9.17.16. Adem\u00e1s, la versi\u00f3n 9.16.19-S1 de BIND Supported Preview Edition. Cuando una versi\u00f3n vulnerable de named recibe una consulta en las circunstancias descritas anteriormente, el proceso named terminar\u00e1 debido a una comprobaci\u00f3n de aserci\u00f3n fallida. La vulnerabilidad s\u00f3lo afecta a versiones 9.16.19, 9.17.16 y 9.16.19-S1 de BIND Supported Preview Edition."}], "id": "CVE-2021-25218", "lastModified": "2023-11-07T03:31:25.027", "metrics": {"cvssMetricV2": [{"acInsufInfo": false, "baseSeverity": "MEDIUM", "cvssData": {"accessComplexity": "LOW", "accessVector": "NETWORK", "authentication": "NONE", "availabilityImpact": "PARTIAL", "baseScore": 5.0, "confidentialityImpact": "NONE", "integrityImpact": "NONE", "vectorString": "AV:N/AC:L/Au:N/C:N/I:N/A:P", "version": "2.0"}, "exploitabilityScore": 10.0, "impactScore": 2.9, "obtainAllPrivilege": false, "obtainOtherPrivilege": false, "obtainUserPrivilege": false, "source": "nvd@nist.gov", "type": "Primary", "userInteractionRequired": false}], "cvssMetricV31": [{"cvssData": {"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"}, "exploitabilityScore": 3.9, "impactScore": 3.6, "source": "nvd@nist.gov", "type": "Primary"}, {"cvssData": {"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"}, "exploitabilityScore": 3.9, "impactScore": 3.6, "source": "security-officer@isc.org", "type": "Secondary"}]}, "published": "2021-08-18T19:15:07.333", "references": [{"source": "security-officer@isc.org", "tags": ["Mailing List", "Patch", "Third Party Advisory"], "url": "http://www.openwall.com/lists/oss-security/2021/08/18/3"}, {"source": "security-officer@isc.org", "tags": ["Mailing List", "Patch", "Third Party Advisory"], "url": "http://www.openwall.com/lists/oss-security/2021/08/20/2"}, {"source": "security-officer@isc.org", "tags": ["Exploit", "Vendor Advisory"], "url": "https://kb.isc.org/v1/docs/cve-2021-25218"}, {"source": "security-officer@isc.org", "url": "https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZPJCLGSR4BTGFLBLGIE5TEQP2SNJKGVL/"}, {"source": "security-officer@isc.org", "tags": ["Third Party Advisory"], "url": "https://security.netapp.com/advisory/ntap-20210909-0002/"}], "sourceIdentifier": "security-officer@isc.org", "vulnStatus": "Modified", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-617"}], "source": "nvd@nist.gov", "type": "Primary"}]}

{"bugzilla": {"description": "bind: Too strict assertion check could be triggered when responses require UDP fragmentation if RRL is in use", "id": "1995312", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=1995312"}, "csaw": false, "cvss3": {"cvss3_base_score": "7.5", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "status": "draft"}, "cwe": "CWE-617", "details": ["In BIND 9.16.19, 9.17.16. Also, version 9.16.19-S1 of BIND Supported Preview Edition When a vulnerable version of named receives a query under the circumstances described above, the named process will terminate due to a failed assertion check. The vulnerability affects only BIND 9 releases 9.16.19, 9.17.16, and release 9.16.19-S1 of the BIND Supported Preview Edition.", "A flaw was found in bind. An assertion failure is triggered, resulting in termination of the named server process, if named attempts to respond over UDP with a response that is larger than the current effective interface maximum transmission unit (MTU), and if response-rate limiting (RRL) is active. The highest threat from this vulnerability is to system availability."], "mitigation": {"lang": "en:us", "value": "Disabling RRL in all views, including the builtin CHAOS class view, prevents the faulty assertion from being reached in the vulnerable versions of bind. To do that you can remove `rate-limit` from your named.conf files and provide a replacement for the builtin CHAOS view, like the one below:\n```\nview override_bind chaos {\nrecursion no;\nnotify no;\nallow-new-zones no;\nmax-cache-size 2M;\nzone \"version.bind\" chaos {\ntype primary;\ndatabase \"_builtin version\";\n};\nzone \"hostname.bind\" chaos {\ntype primary;\ndatabase \"_builtin hostname\";\n};\nzone \"authors.bind\" chaos {\ntype primary;\ndatabase \"_builtin authors\";\n};\nzone \"id.server\" chaos {\ntype primary;\ndatabase \"_builtin id\";\n};\n};\n```"}, "name": "CVE-2021-25218", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Not affected", "package_name": "bind", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "bind", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "bind", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "bind", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:rhev_hypervisor:4", "fix_state": "Not affected", "package_name": "redhat-virtualization-host", "product_name": "Red Hat Virtualization 4"}], "public_date": "2021-08-18T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2021-25218\nhttps://nvd.nist.gov/vuln/detail/CVE-2021-25218\nhttps://kb.isc.org/docs/cve-2021-25218"], "statement": "An attacker may abuse the Path MTU discovery (PMTUD) protocol to trick bind into exceeding the interface MTU. Response Rate Limiting (RRL) is not enabled by default for user defined views nor the builtin one, but it is enabled by default for the default builtin CHAOS class view, which bind uses to provide various information.\nThis issue did not affect the versions of bind as shipped with Red Hat Enterprise Linux 6, 7, and 8 as they provide an older version of the code which does not allow to trigger the assertion.", "threat_severity": "Important", "upstream_fix": "bind 9.16.20, bind 9.17.17, bind 9.16.20-S1"}