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CVE-2020-25686

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Date: January 20, 2021

A flaw was found in dnsmasq before version 2.83. 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.

Language: C

Severity Score

Related Resources (20)

https://security.archlinux.org/CVE-2020-25686
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/WYW3IR6APUSKOYKL5FT3ACTIHWHGQY32/
https://security.gentoo.org/glsa/202101-17
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/QGB7HL3OWHTLEPSMLDGOMXQKG3KM2QME/
https://access.redhat.com/security/cve/CVE-2020-25686
http://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=commit;h=6a6e06fbb0d4690507ceaf2bb6f0d8910f3d4914
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WYW3IR6APUSKOYKL5FT3ACTIHWHGQY32/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QGB7HL3OWHTLEPSMLDGOMXQKG3KM2QME/
http://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=commitdiff;h=6a6e06fbb0d4690507ceaf2bb6f0d8910f3d4914;hp=2024f9729713fd657d65e64c2e4e471baa0a3e5b
http://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=commitdiff;h=15b60ddf935a531269bb8c68198de012a4967156;hp=824461192ca5098043f9ca4ddeba7df1f65b30ba
http://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=commit;h=15b60ddf935a531269bb8c68198de012a4967156
https://nvd.nist.gov/vuln/detail/CVE-2020-25686
https://bugzilla.redhat.com/show_bug.cgi?id=1890125
https://www.arista.com/en/support/advisories-notices/security-advisories/12135-security-advisory-61
https://www.jsof-tech.com/disclosures/dnspooq/
https://people.canonical.com/~ubuntu-security/cve/CVE-2020-25686
https://security.alpinelinux.org/vuln/CVE-2020-25686
https://security-tracker.debian.org/tracker/CVE-2020-25686
https://www.debian.org/security/2021/dsa-4844
https://www.mend.io/vulnerability-database/CVE-2020-25686

Severity Score

Weakness Type (CWE)

Improperly Implemented Security Check for Standard

CWE-358

Authentication Bypass by Spoofing

CWE-290

Top Fix

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CVSS v3.1

Base Score:
Attack Vector (AV): NETWORK
Attack Complexity (AC): HIGH
Privileges Required (PR): NONE
User Interaction (UI): NONE
Scope (S): UNCHANGED
Confidentiality (C): NONE
Integrity (I): LOW
Availability (A): NONE

CVSS v2

Base Score:
Access Vector (AV): NETWORK
Access Complexity (AC): MEDIUM
Authentication (AU): NONE
Confidentiality (C): NONE
Integrity (I): PARTIAL
Availability (A): NONE
Additional information:

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