{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"state": "PUBLISHED", "cveId": "CVE-2020-25685", "assignerOrgId": "53f830b8-0a3f-465b-8143-3b8a9948e749", "assignerShortName": "redhat", "dateUpdated": "2025-11-04T19:12:13.209Z", "dateReserved": "2020-09-16T00:00:00.000Z", "datePublished": "2021-01-20T00:00:00.000Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "53f830b8-0a3f-465b-8143-3b8a9948e749", "shortName": "redhat", "dateUpdated": "2022-10-07T00:00:00.000Z"}, "descriptions": [{"lang": "en", "value": "A flaw was found in dnsmasq before version 2.83. When getting a reply from a forwarded query, dnsmasq checks in forward.c:reply_query(), which is the forwarded query that matches the reply, by only using a weak hash of the query name. Due to the weak hash (CRC32 when dnsmasq is compiled without DNSSEC, SHA-1 when it is) this flaw allows an off-path attacker to find several different domains all having the same hash, substantially reducing the number of attempts they would have to perform to forge a reply and get it accepted by dnsmasq. This is in contrast with RFC5452, which specifies that the query name is one of the attributes of a query that must be used to match a reply. This flaw could be abused to perform a DNS Cache Poisoning attack. If chained with CVE-2020-25684 the attack complexity of a successful attack is reduced. The highest threat from this vulnerability is to data integrity."}], "affected": [{"vendor": "n/a", "product": "dnsmasq", "versions": [{"version": "dnsmasq 2.83", "status": "affected"}]}], "references": [{"url": "https://www.jsof-tech.com/disclosures/dnspooq/"}, {"url": "https://bugzilla.redhat.com/show_bug.cgi?id=1889688"}, {"name": "FEDORA-2021-84440e87ba", "tags": ["vendor-advisory"], "url": "https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WYW3IR6APUSKOYKL5FT3ACTIHWHGQY32/"}, {"name": "GLSA-202101-17", "tags": ["vendor-advisory"], "url": "https://security.gentoo.org/glsa/202101-17"}, {"name": "DSA-4844", "tags": ["vendor-advisory"], "url": "https://www.debian.org/security/2021/dsa-4844"}, {"name": "FEDORA-2021-2e4c3d5a9d", "tags": ["vendor-advisory"], "url": "https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QGB7HL3OWHTLEPSMLDGOMXQKG3KM2QME/"}, {"url": "https://www.arista.com/en/support/advisories-notices/security-advisories/12135-security-advisory-61"}], "problemTypes": [{"descriptions": [{"type": "CWE", "lang": "en", "description": "CWE-326", "cweId": "CWE-326"}]}]}, "adp": [{"title": "CVE Program Container", "references": [{"url": "https://www.jsof-tech.com/disclosures/dnspooq/", "tags": ["x_transferred"]}, {"url": "https://bugzilla.redhat.com/show_bug.cgi?id=1889688", "tags": ["x_transferred"]}, {"name": "FEDORA-2021-84440e87ba", "tags": ["vendor-advisory", "x_transferred"], "url": "https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WYW3IR6APUSKOYKL5FT3ACTIHWHGQY32/"}, {"name": "GLSA-202101-17", "tags": ["vendor-advisory", "x_transferred"], "url": "https://security.gentoo.org/glsa/202101-17"}, {"name": "DSA-4844", "tags": ["vendor-advisory", "x_transferred"], "url": "https://www.debian.org/security/2021/dsa-4844"}, {"name": "FEDORA-2021-2e4c3d5a9d", "tags": ["vendor-advisory", "x_transferred"], "url": "https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QGB7HL3OWHTLEPSMLDGOMXQKG3KM2QME/"}, {"url": "https://www.arista.com/en/support/advisories-notices/security-advisories/12135-security-advisory-61", "tags": ["x_transferred"]}, {"url": "https://www.kb.cert.org/vuls/id/434904"}], "providerMetadata": {"orgId": "af854a3a-2127-422b-91ae-364da2661108", "shortName": "CVE", "dateUpdated": "2025-11-04T19:12:13.209Z"}}]}}

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When getting a reply from a forwarded query, dnsmasq checks in forward.c:reply_query(), which is the forwarded query that matches the reply, by only using a weak hash of the query name. Due to the weak hash (CRC32 when dnsmasq is compiled without DNSSEC, SHA-1 when it is) this flaw allows an off-path attacker to find several different domains all having the same hash, substantially reducing the number of attempts they would have to perform to forge a reply and get it accepted by dnsmasq. This is in contrast with RFC5452, which specifies that the query name is one of the attributes of a query that must be used to match a reply. This flaw could be abused to perform a DNS Cache Poisoning attack. If chained with CVE-2020-25684 the attack complexity of a successful attack is reduced. The highest threat from this vulnerability is to data integrity."}, {"lang": "es", "value": "Se encontr\u00f3 un fallo en dnsmasq versiones anteriores a 2.83. Al obtener una respuesta de una consulta reenviada, dnsmasq comprueba en forward.c:reply_query(), que es la consulta reenviada que coincide con la respuesta, usando solo un hash d\u00e9bil del nombre de la consulta. Debido al hash d\u00e9bil (CRC32 cuando dnsmasq se compila sin DNSSEC, SHA-1 cuando lo es), este fallo permite a un atacante fuera de ruta encontrar varios dominios diferentes que tengan el mismo hash, reduciendo sustancialmente el n\u00famero de intentos que tendr\u00edan que realizar para falsificar una respuesta y conseguir que dnsmasq la acepte. Esto contrasta con RFC5452, que especifica que el nombre de la consulta es uno de los atributos de una consulta que debe ser usada para hacer coincidir una respuesta. Se puede abusar de este fallo para realizar un ataque de envenenamiento de cach\u00e9 de DNS. Si se encadena con CVE-2020-25684, se reduce la complejidad del ataque de un ataque con \u00e9xito"}], "id": "CVE-2020-25685", "lastModified": "2025-11-04T20:15:57.363", "metrics": {"cvssMetricV2": [{"acInsufInfo": false, "baseSeverity": "MEDIUM", "cvssData": {"accessComplexity": "MEDIUM", "accessVector": "NETWORK", "authentication": "NONE", "availabilityImpact": "NONE", "baseScore": 4.3, "confidentialityImpact": "NONE", "integrityImpact": "PARTIAL", "vectorString": "AV:N/AC:M/Au:N/C:N/I:P/A:N", "version": "2.0"}, "exploitabilityScore": 8.6, "impactScore": 2.9, "obtainAllPrivilege": false, "obtainOtherPrivilege": false, "obtainUserPrivilege": false, "source": "nvd@nist.gov", "type": "Primary", "userInteractionRequired": false}], "cvssMetricV31": [{"cvssData": {"attackComplexity": "HIGH", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 3.7, "baseSeverity": "LOW", "confidentialityImpact": "NONE", "integrityImpact": "LOW", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N", "version": "3.1"}, "exploitabilityScore": 2.2, "impactScore": 1.4, "source": "nvd@nist.gov", "type": "Primary"}]}, "published": "2021-01-20T16:15:14.303", "references": [{"source": "secalert@redhat.com", "tags": ["Issue Tracking", "Patch", "Third Party Advisory"], "url": "https://bugzilla.redhat.com/show_bug.cgi?id=1889688"}, {"source": "secalert@redhat.com", "url": "https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QGB7HL3OWHTLEPSMLDGOMXQKG3KM2QME/"}, {"source": "secalert@redhat.com", "url": "https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WYW3IR6APUSKOYKL5FT3ACTIHWHGQY32/"}, {"source": "secalert@redhat.com", "tags": ["Third Party Advisory"], "url": "https://security.gentoo.org/glsa/202101-17"}, {"source": "secalert@redhat.com", "tags": ["Third Party Advisory"], "url": "https://www.arista.com/en/support/advisories-notices/security-advisories/12135-security-advisory-61"}, {"source": "secalert@redhat.com", "tags": ["Third Party Advisory"], "url": "https://www.debian.org/security/2021/dsa-4844"}, {"source": "secalert@redhat.com", "tags": ["Third Party Advisory"], "url": "https://www.jsof-tech.com/disclosures/dnspooq/"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Issue Tracking", "Patch", "Third Party Advisory"], "url": "https://bugzilla.redhat.com/show_bug.cgi?id=1889688"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "url": "https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QGB7HL3OWHTLEPSMLDGOMXQKG3KM2QME/"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "url": "https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WYW3IR6APUSKOYKL5FT3ACTIHWHGQY32/"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Third Party Advisory"], "url": "https://security.gentoo.org/glsa/202101-17"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Third Party Advisory"], "url": "https://www.arista.com/en/support/advisories-notices/security-advisories/12135-security-advisory-61"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Third Party Advisory"], "url": "https://www.debian.org/security/2021/dsa-4844"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Third Party Advisory"], "url": "https://www.jsof-tech.com/disclosures/dnspooq/"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "url": "https://www.kb.cert.org/vuls/id/434904"}], "sourceIdentifier": "secalert@redhat.com", "vulnStatus": "Modified", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-326"}], "source": "secalert@redhat.com", "type": "Secondary"}, {"description": [{"lang": "en", "value": "CWE-326"}], "source": "nvd@nist.gov", "type": "Primary"}]}

{"acknowledgement": "Red Hat would like to thank Moshe Kol (JSOF) and Shlomi Oberman (JSOF) for reporting this issue.", "affected_release": [{"advisory": "RHSA-2021:0153", "cpe": "cpe:/o:redhat:enterprise_linux:7", "package": "dnsmasq-0:2.76-16.el7_9.1", "product_name": "Red Hat Enterprise Linux 7", "release_date": "2021-01-19T00:00:00Z"}, {"advisory": "RHSA-2021:0240", "cpe": "cpe:/o:redhat:rhel_aus:7.2", "package": "dnsmasq-0:2.66-14.el7_2.3", "product_name": "Red Hat Enterprise Linux 7.2 Advanced Update Support", "release_date": "2021-01-25T00:00:00Z"}, {"advisory": "RHSA-2021:0245", "cpe": "cpe:/o:redhat:rhel_aus:7.3", "package": "dnsmasq-0:2.66-21.el7_3.3", "product_name": "Red Hat Enterprise Linux 7.3 Advanced Update Support", "release_date": "2021-01-25T00:00:00Z"}, {"advisory": "RHSA-2021:0156", "cpe": "cpe:/o:redhat:rhel_aus:7.4", "package": "dnsmasq-0:2.76-2.el7_4.3", "product_name": "Red Hat Enterprise Linux 7.4 Advanced Update Support", "release_date": "2021-01-19T00:00:00Z"}, {"advisory": "RHSA-2021:0156", "cpe": "cpe:/o:redhat:rhel_tus:7.4", "package": "dnsmasq-0:2.76-2.el7_4.3", "product_name": "Red Hat Enterprise Linux 7.4 Telco Extended Update Support", "release_date": "2021-01-19T00:00:00Z"}, {"advisory": "RHSA-2021:0156", "cpe": "cpe:/o:redhat:rhel_e4s:7.4", "package": "dnsmasq-0:2.76-2.el7_4.3", "product_name": "Red Hat Enterprise Linux 7.4 Update Services for SAP Solutions", "release_date": "2021-01-19T00:00:00Z"}, {"advisory": "RHSA-2021:0155", "cpe": "cpe:/o:redhat:rhel_eus:7.6", "package": "dnsmasq-0:2.76-7.el7_6.2", "product_name": "Red Hat Enterprise Linux 7.6 Extended Update Support", "release_date": "2021-01-19T00:00:00Z"}, {"advisory": "RHSA-2021:0154", "cpe": "cpe:/o:redhat:rhel_eus:7.7", "package": "dnsmasq-0:2.76-10.el7_7.2", "product_name": "Red Hat Enterprise Linux 7.7 Extended Update Support", "release_date": "2021-01-19T00:00:00Z"}, {"advisory": "RHSA-2021:0150", "cpe": "cpe:/a:redhat:enterprise_linux:8", "package": "dnsmasq-0:2.79-13.el8_3.1", "product_name": "Red Hat Enterprise Linux 8", "release_date": "2021-01-19T00:00:00Z"}, {"advisory": "RHSA-2021:0152", "cpe": "cpe:/a:redhat:rhel_eus:8.1", "package": "dnsmasq-0:2.79-6.el8_1.1", "product_name": "Red Hat Enterprise Linux 8.1 Extended Update Support", "release_date": "2021-01-19T00:00:00Z"}, {"advisory": "RHSA-2021:0151", "cpe": "cpe:/a:redhat:rhel_eus:8.2", "package": "dnsmasq-0:2.79-11.el8_2.2", "product_name": "Red Hat Enterprise Linux 8.2 Extended Update Support", "release_date": "2021-01-19T00:00:00Z"}, {"advisory": "RHSA-2021:0395", "cpe": "cpe:/o:redhat:enterprise_linux:7::hypervisor", "package": "redhat-virtualization-host-0:4.3.13-20210127.0.el7_9", "product_name": "Red Hat Virtualization 4 for Red Hat Enterprise Linux 7", "release_date": "2021-02-03T00:00:00Z"}, {"advisory": "RHSA-2021:0401", "cpe": "cpe:/o:redhat:rhev_hypervisor:4.4::el8", "package": "redhat-virtualization-host-0:4.4.4-20210201.0.el8_3", "product_name": "Red Hat Virtualization 4 for Red Hat Enterprise Linux 8", "release_date": "2021-02-03T00:00:00Z"}], "bugzilla": {"description": "dnsmasq: loose query name check in reply_query() makes forging replies easier for an off-path attacker", "id": "1889688", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=1889688"}, "csaw": true, "cvss3": {"cvss3_base_score": "4.0", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:N", "status": "verified"}, "cwe": "CWE-326", "details": ["A flaw was found in dnsmasq before version 2.83. When getting a reply from a forwarded query, dnsmasq checks in forward.c:reply_query(), which is the forwarded query that matches the reply, by only using a weak hash of the query name. Due to the weak hash (CRC32 when dnsmasq is compiled without DNSSEC, SHA-1 when it is) this flaw allows an off-path attacker to find several different domains all having the same hash, substantially reducing the number of attempts they would have to perform to forge a reply and get it accepted by dnsmasq. This is in contrast with RFC5452, which specifies that the query name is one of the attributes of a query that must be used to match a reply. This flaw could be abused to perform a DNS Cache Poisoning attack. If chained with CVE-2020-25684 the attack complexity of a successful attack is reduced. The highest threat from this vulnerability is to data integrity.", "A flaw was found in dnsmasq. When getting a reply from a forwarded query, dnsmasq checks in forward.c:reply_query(), which is the forwarded query that matches the reply, by only using a weak hash of the query name. Due to the weak hash (CRC32 when dnsmasq is compiled without DNSSEC, SHA-1 when it is) this flaw allows an off-path attacker to find several different domains all having the same hash, substantially reducing the number of attempts they would have to perform to forge a reply and get it accepted by dnsmasq. This is in contrast with RFC5452, which specifies that the query name is one of the attributes of a query that must be used to match a reply. This flaw could be abused to perform a DNS Cache Poisoning attack. If chained with CVE-2020-25684 the attack complexity of a successful attack is reduced. The highest threat from this vulnerability is to data integrity."], "mitigation": {"lang": "en:us", "value": "The impact of this flaw can be reduced by disabling the dnsmasq cache by adding `--cache-size=0` when calling dnsmasq or by adding a line with `cache-size=0` to the dnsmasq configuration file (/etc/dnsmasq.conf by default). \nWhen using Red Hat Enterprise Linux 8.3 with libvirt through a virt:rhel module, use `virsh net-edit <network-name>` and reference https://libvirt.org/formatnetwork.html#elementsNamespaces to add the suggested option `cache-size=0`. \nThere is no way to customize the dnsmasq configuration generated by libvirt, when using versions of Red Hat Enterprise Linux prior to version 8.3. If dnsmasq is being run through NetworkManager, create a new file in /etc/NetworkManager/dnsmasq.d/ and add `cache-size=0` to it.\nIn all cases, by disabling the cache, you may experience a performance loss in your environment due to all DNS queries being forwarded to the upstream servers. Please evaluate if the mitigation is appropriate for the system\u2019s environment before applying."}, "name": "CVE-2020-25685", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:5", "fix_state": "Out of support scope", "package_name": "dnsmasq", "product_name": "Red Hat Enterprise Linux 5"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Out of support scope", "package_name": "dnsmasq", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "dnsmasq", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/a:redhat:openstack:10", "fix_state": "Not affected", "package_name": "dnsmasq", "product_name": "Red Hat OpenStack Platform 10 (Newton)"}, {"cpe": "cpe:/a:redhat:openstack:13", "fix_state": "Not affected", "package_name": "dnsmasq", "product_name": "Red Hat OpenStack Platform 13 (Queens)"}], "public_date": "2021-01-19T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2020-25685\nhttps://nvd.nist.gov/vuln/detail/CVE-2020-25685\nhttps://www.jsof-tech.com/disclosures/dnspooq/"], "statement": "Dnsmasq may be run by libvirt and/or NetworkManager. libvirt uses dnsmasq by default to provide DNS service to its guests. NetworkManager may be configured to use dnsmasq to provide DNS service to the system, if a line `dns=dnsmasq` is present in the `[main]` section of the configuration file /etc/NetworkManager/NetworkManager.conf.\nIn Red Hat OpenStack Platform (RHOSP) and Red Hat Virtualization (RHV), the dnsmasq package is provided by the underlying Red Hat Enterprise Linux (RHEL) product. RHOSP and RHV are therefore indirectly affected, so please ensure that the underlying RHEL dnsmasq package is updated.", "threat_severity": "Moderate"}