# CVE-2020-25685: dnsmasq: A flaw was found in dnsmasq before version 2.83 CVE-2020-25685 is fixed in 4 products on 1 platform, first by dnsmasq 2.79-1ubuntu0.2, released January 18, 2021. It is not reported as exploited. Patch Radar priority: Routine. - Web page: https://patchblox.com/security/cve/CVE-2020-25685 - Priority: Routine - CVSS: 4.0 (Medium) - EPSS: 0.0223 - CISA KEV: not listed - Exploited (vendor report): no - Publicly disclosed: no - Published: Jan 18, 2021 ## Description A flaw was found in dnsmasq before version 2.83. When getting a reply froma forwarded query, dnsmasq checks in forward.c:reply_query(), which is theforwarded query that matches the reply, by only using a weak hash of thequery name. Due to the weak hash (CRC32 when dnsmasq is compiled withoutDNSSEC, SHA-1 when it is) this flaw allows an off-path attacker to findseveral different domains all having the same hash, substantially reducingthe number of attempts they would have to perform to forge a reply and getit accepted by dnsmasq. This is in contrast with RFC5452, which specifiesthat the query name is one of the attributes of a query that must be usedto match a reply. This flaw could be abused to perform a DNS CachePoisoning attack. If chained with CVE-2020-25684 the attack complexity of asuccessful attack is reduced. The highest threat from this vulnerability isto data integrity. ## Where it's fixed | Platform | Product | Fixed in | Fix | Released | |---|---|---|---|---| | Linux | dnsmasq RHEL 8 | 0:2.79-13.el8_3.1 | [RHSA-2021:0150](https://patchblox.com/security/data/fix/linux/rhsa-2021-0150.md) | Jan 19, 2021 | | Linux | dnsmasq Ubuntu 18.04.6 LTS (bionic) | 2.79-1ubuntu0.2 | [dnsmasq 2.79-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-dnsmasq-2.79-1ubuntu0.2.md) | Jan 18, 2021 | | Linux | dnsmasq Ubuntu 20.04 LTS (focal) | 2.80-1.1ubuntu1.2 | [dnsmasq 2.80-1.1ubuntu1.2](https://patchblox.com/security/data/fix/linux/ubuntu-focal-dnsmasq-2.80-1.1ubuntu1.2.md) | Jan 18, 2021 | | Linux | dnsmasq Ubuntu 24.10 (oracular) | 2.82-1ubuntu2 | [dnsmasq 2.82-1ubuntu2](https://patchblox.com/security/data/fix/linux/ubuntu-oracular-dnsmasq-2.82-1ubuntu2.md) | Jan 19, 2021 | | Linux | dnsmasq Ubuntu 25.04 (plucky) | 2.82-1ubuntu2 | [dnsmasq 2.82-1ubuntu2](https://patchblox.com/security/data/fix/linux/ubuntu-plucky-dnsmasq-2.82-1ubuntu2.md) | Jan 19, 2021 | | Linux | dnsmasq ol 8 | 0:2.79-13.el8_3.1 | [ELSA-2021-0150](https://patchblox.com/security/data/fix/linux/elsa-2021-0150.md) | Jan 20, 2021 | | Linux | dnsmasq-base Ubuntu 18.04.6 LTS (bionic) | 2.79-1ubuntu0.2 | [dnsmasq-base 2.79-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-dnsmasq-base-2.79-1ubuntu0.2.md) | Jan 18, 2021 | | Linux | dnsmasq-base Ubuntu 20.04 LTS (focal) | 2.80-1.1ubuntu1.2 | [dnsmasq-base 2.80-1.1ubuntu1.2](https://patchblox.com/security/data/fix/linux/ubuntu-focal-dnsmasq-base-2.80-1.1ubuntu1.2.md) | Jan 18, 2021 | | Linux | dnsmasq-base Ubuntu 24.10 (oracular) | 2.82-1ubuntu2 | [dnsmasq-base 2.82-1ubuntu2](https://patchblox.com/security/data/fix/linux/ubuntu-oracular-dnsmasq-base-2.82-1ubuntu2.md) | Jan 19, 2021 | | Linux | dnsmasq-base Ubuntu 25.04 (plucky) | 2.82-1ubuntu2 | [dnsmasq-base 2.82-1ubuntu2](https://patchblox.com/security/data/fix/linux/ubuntu-plucky-dnsmasq-base-2.82-1ubuntu2.md) | Jan 19, 2021 | | Linux | dnsmasq-base-lua Ubuntu 18.04.6 LTS (bionic) | 2.79-1ubuntu0.2 | [dnsmasq-base-lua 2.79-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-dnsmasq-base-lua-2.79-1ubuntu0.2.md) | Jan 18, 2021 | | Linux | dnsmasq-base-lua Ubuntu 20.04 LTS (focal) | 2.80-1.1ubuntu1.2 | [dnsmasq-base-lua 2.80-1.1ubuntu1.2](https://patchblox.com/security/data/fix/linux/ubuntu-focal-dnsmasq-base-lua-2.80-1.1ubuntu1.2.md) | Jan 18, 2021 | | Linux | dnsmasq-base-lua Ubuntu 24.10 (oracular) | 2.82-1ubuntu2 | [dnsmasq-base-lua 2.82-1ubuntu2](https://patchblox.com/security/data/fix/linux/ubuntu-oracular-dnsmasq-base-lua-2.82-1ubuntu2.md) | Jan 19, 2021 | | Linux | dnsmasq-base-lua Ubuntu 25.04 (plucky) | 2.82-1ubuntu2 | [dnsmasq-base-lua 2.82-1ubuntu2](https://patchblox.com/security/data/fix/linux/ubuntu-plucky-dnsmasq-base-lua-2.82-1ubuntu2.md) | Jan 19, 2021 | | Linux | dnsmasq-utils RHEL 8 | 0:2.79-13.el8_3.1 | [RHSA-2021:0150](https://patchblox.com/security/data/fix/linux/rhsa-2021-0150.md) | Jan 19, 2021 | | Linux | dnsmasq-utils Ubuntu 18.04.6 LTS (bionic) | 2.79-1ubuntu0.2 | [dnsmasq-utils 2.79-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-dnsmasq-utils-2.79-1ubuntu0.2.md) | Jan 18, 2021 | | Linux | dnsmasq-utils Ubuntu 20.04 LTS (focal) | 2.80-1.1ubuntu1.2 | [dnsmasq-utils 2.80-1.1ubuntu1.2](https://patchblox.com/security/data/fix/linux/ubuntu-focal-dnsmasq-utils-2.80-1.1ubuntu1.2.md) | Jan 18, 2021 | | Linux | dnsmasq-utils Ubuntu 24.10 (oracular) | 2.82-1ubuntu2 | [dnsmasq-utils 2.82-1ubuntu2](https://patchblox.com/security/data/fix/linux/ubuntu-oracular-dnsmasq-utils-2.82-1ubuntu2.md) | Jan 19, 2021 | | Linux | dnsmasq-utils Ubuntu 25.04 (plucky) | 2.82-1ubuntu2 | [dnsmasq-utils 2.82-1ubuntu2](https://patchblox.com/security/data/fix/linux/ubuntu-plucky-dnsmasq-utils-2.82-1ubuntu2.md) | Jan 19, 2021 | | Linux | dnsmasq-utils ol 8 | 0:2.79-13.el8_3.1 | [ELSA-2021-0150](https://patchblox.com/security/data/fix/linux/elsa-2021-0150.md) | Jan 20, 2021 | --- Data as of 2026-11-08T00:53:09Z UTC. 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