Bug 1890125 (CVE-2020-25686)
| Summary: | CVE-2020-25686 dnsmasq: multiple queries forwarded for the same name makes forging replies easier for an off-path attacker | ||
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| Product: | [Other] Security Response | Reporter: | Riccardo Schirone <rschiron> |
| Component: | vulnerability | Assignee: | Red Hat Product Security <security-response-team> |
| Status: | CLOSED ERRATA | QA Contact: | |
| Severity: | medium | Docs Contact: | |
| Priority: | medium | ||
| Version: | unspecified | CC: | aegorenk, code, dbecker, dblechte, dfediuck, dns-sig, dougsland, eedri, emarcus, itamar, jima, jjoyce, jschluet, jsvoboda, laine, lhh, lpeer, mburns, mgoldboi, michal.skrivanek, nlevy, pemensik, sbonazzo, sclewis, security-response-team, sherold, slinaber, veillard, yturgema |
| Target Milestone: | --- | Keywords: | Security |
| Target Release: | --- | ||
| Hardware: | All | ||
| OS: | Linux | ||
| Whiteboard: | |||
| Fixed In Version: | dnsmasq 2.83 | Doc Type: | Known Issue |
| Doc Text: |
A flaw was found in dnsmasq. When receiving a query, dnsmasq does not check for an existing pending request for the same name and forwards a new request. By default, a maximum of 150 pending queries can be sent to upstream servers, so there can be at most 150 queries for the same name. This flaw allows an off-path attacker on the network to substantially reduce the number of attempts that it would have to perform to forge a reply and have it accepted by dnsmasq. This issue is mentioned in the "Birthday Attacks" section of RFC5452. 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.
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Story Points: | --- |
| Clone Of: | Environment: | ||
| Last Closed: | 2021-01-19 17:59:29 UTC | Type: | --- |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
| Embargoed: | |||
| Bug Depends On: | 1896063, 1896066, 1896068, 1896070, 1896072, 1896073, 1896074, 1896075, 1905021, 1905022, 1905023, 1917321, 1917322, 1917787, 1917793, 1918955, 1918956 | ||
| Bug Blocks: | 1875522 | ||
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Description
Riccardo Schirone
2020-10-21 13:07:53 UTC
OSD3 services are using dnsmasq shipped directly by RHEL7, each node has its own dnsmasq Red Hat Enterprise Linux 5, 6, 7, and 8 are all affected in the same way and the same mitigations apply. Mitigation: 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). When 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`. There 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. In 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’s environment before applying. 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. In 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. Acknowledgments: Name: Moshe Kol (JSOF), Shlomi Oberman (JSOF) External References: https://www.jsof-tech.com/disclosures/dnspooq/ Created dnsmasq tracking bugs for this issue: Affects: fedora-all [bug 1917787] This issue has been addressed in the following products: Red Hat Enterprise Linux 8.1 Extended Update Support Via RHSA-2021:0152 https://access.redhat.com/errata/RHSA-2021:0152 This issue has been addressed in the following products: Red Hat Enterprise Linux 8 Via RHSA-2021:0150 https://access.redhat.com/errata/RHSA-2021:0150 Upstream patches: http://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=commit;h=15b60ddf935a531269bb8c68198de012a4967156 http://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=commit;h=6a6e06fbb0d4690507ceaf2bb6f0d8910f3d4914 This issue has been addressed in the following products: Red Hat Enterprise Linux 8.2 Extended Update Support Via RHSA-2021:0151 https://access.redhat.com/errata/RHSA-2021:0151 This issue has been addressed in the following products: Red Hat Enterprise Linux 7.4 Advanced Update Support Red Hat Enterprise Linux 7.4 Update Services for SAP Solutions Red Hat Enterprise Linux 7.4 Telco Extended Update Support Via RHSA-2021:0156 https://access.redhat.com/errata/RHSA-2021:0156 This issue has been addressed in the following products: Red Hat Enterprise Linux 7 Via RHSA-2021:0153 https://access.redhat.com/errata/RHSA-2021:0153 This issue has been addressed in the following products: Red Hat Enterprise Linux 7.7 Extended Update Support Via RHSA-2021:0154 https://access.redhat.com/errata/RHSA-2021:0154 This issue has been addressed in the following products: Red Hat Enterprise Linux 7.6 Extended Update Support Via RHSA-2021:0155 https://access.redhat.com/errata/RHSA-2021:0155 This bug is now closed. Further updates for individual products will be reflected on the CVE page(s): https://access.redhat.com/security/cve/cve-2020-25686 This issue has been addressed in the following products: Red Hat Enterprise Linux 7.2 Advanced Update Support Via RHSA-2021:0240 https://access.redhat.com/errata/RHSA-2021:0240 This issue has been addressed in the following products: Red Hat Enterprise Linux 7.3 Advanced Update Support Via RHSA-2021:0245 https://access.redhat.com/errata/RHSA-2021:0245 This issue has been addressed in the following products: Red Hat Virtualization 4 for Red Hat Enterprise Linux 7 Via RHSA-2021:0395 https://access.redhat.com/errata/RHSA-2021:0395 This issue has been addressed in the following products: Red Hat Virtualization 4 for Red Hat Enterprise Linux 8 Via RHSA-2021:0401 https://access.redhat.com/errata/RHSA-2021:0401 |