Moshe Kol and Shlomi Oberman of JSOF discovered several vulnerabilities in dnsmasq, a small caching DNS proxy and DHCP/TFTP server. They could result in denial of service, cache poisoning or the execution of arbitrary code.

According to the versions of the dnsmasq packages installed, the EulerOS installation on the remote host is affected by the following vulnerabilities :

  - A flaw was found in dnsmasq before version 2.83. A     heap-based buffer overflow was discovered in the way     RRSets are sorted before validating with DNSSEC data.
    An attacker on the network, who can forge DNS replies     such as that they are accepted as valid, could use this     flaw to cause a buffer overflow with arbitrary data in     a heap memory segment, possibly executing code on the     machine. The highest threat from this vulnerability is     to data confidentiality and integrity as well as system     availability.(CVE-2020-25681)

  - A flaw was found in dnsmasq before 2.83. A buffer     overflow vulnerability was discovered in the way     dnsmasq extract names from DNS packets before     validating them with DNSSEC data. An attacker on the     network, who can create valid DNS replies, could use     this flaw to cause an overflow with arbitrary data in a     heap-allocated memory, possibly executing code on the     machine. The flaw is in the rfc1035.c:extract_name()     function, which writes data to the memory pointed by     name assuming MAXDNAME*2 bytes are available in the     buffer. However, in some code execution paths, it is     possible extract_name() gets passed an offset from the     base buffer, thus reducing, in practice, the number of     available bytes that can be written in the buffer. The     highest threat from this vulnerability is to data     confidentiality and integrity as well as system     availability.(CVE-2020-25682)

  - A flaw was found in dnsmasq before version 2.83. A     heap-based buffer overflow was discovered in dnsmasq     when DNSSEC is enabled and before it validates the     received DNS entries. A remote attacker, who can create     valid DNS replies, could use this flaw to cause an     overflow in a heap-allocated memory. This flaw is     caused by the lack of length checks in     rfc1035.c:extract_name(), which could be abused to make     the code execute memcpy() with a negative size in     get_rdata() and cause a crash in dnsmasq, resulting in     a denial of service. The highest threat from this     vulnerability is to system     availability.(CVE-2020-25683)

  - A flaw was found in dnsmasq before version 2.83. When     getting a reply from a forwarded query, dnsmasq checks     in the forward.c:reply_query() if the reply destination     address/port is used by the pending forwarded queries.
    However, it does not use the address/port to retrieve     the exact forwarded query, substantially reducing the     number of attempts an attacker on the network would     have to perform to forge a reply and get it accepted by     dnsmasq. This issue contrasts with RFC5452, which     specifies a query's attributes that all must be used to     match a reply. This flaw allows an attacker to perform     a DNS Cache Poisoning attack. If chained with     CVE-2020-25685 or CVE-2020-25686, the attack complexity     of a successful attack is reduced. The highest threat     from this vulnerability is to data     integrity.(CVE-2020-25684)

  - 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.(CVE-2020-25685)

  - 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.(CVE-2020-25686)

  - A flaw was found in dnsmasq before version 2.83. A     heap-based buffer overflow was discovered in dnsmasq     when DNSSEC is enabled and before it validates the     received DNS entries. This flaw allows a remote     attacker, who can create valid DNS replies, to cause an     overflow in a heap-allocated memory. This flaw is     caused by the lack of length checks in     rfc1035.c:extract_name(), which could be abused to make     the code execute memcpy() with a negative size in     sort_rrset() and cause a crash in dnsmasq, resulting in     a denial of service. The highest threat from this     vulnerability is to system     availability.(CVE-2020-25687)

Note that Tenable Network Security has extracted the preceding description block directly from the EulerOS security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

This plugin has been deprecated as it does not adhere to established standards for this style of check.

The remote Scientific Linux 7 host has packages installed that are affected by multiple vulnerabilities as referenced in the SLSA-2021:0153-1 advisory.

  - dnsmasq: loose address/port check in reply_query() makes forging replies easier for an off-path attacker     (CVE-2020-25684)

  - dnsmasq: loose query name check in reply_query() makes forging replies easier for an off-path attacker     (CVE-2020-25685)

  - dnsmasq: multiple queries forwarded for the same name makes forging replies easier for an off-path     attacker (CVE-2020-25686)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The remote Redhat Enterprise Linux 7 host has packages installed that are affected by multiple vulnerabilities as referenced in the RHSA-2021:0154 advisory.

    The dnsmasq packages contain Dnsmasq, a lightweight DNS (Domain Name Server) forwarder and DHCP (Dynamic     Host Configuration Protocol) server.

    Security Fix(es):

    * dnsmasq: loose address/port check in reply_query() makes forging replies easier for an off-path attacker     (CVE-2020-25684)

    * dnsmasq: loose query name check in reply_query() makes forging replies easier for an off-path attacker     (CVE-2020-25685)

    * dnsmasq: multiple queries forwarded for the same name makes forging replies easier for an off-path     attacker (CVE-2020-25686)

    For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and     other related information, refer to the CVE page(s) listed in the References section.

Tenable has extracted the preceding description block directly from the Red Hat Enterprise Linux security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Redhat Enterprise Linux 7 host has packages installed that are affected by multiple vulnerabilities as referenced in the RHSA-2021:0156 advisory.

    The dnsmasq packages contain Dnsmasq, a lightweight DNS (Domain Name Server) forwarder and DHCP (Dynamic     Host Configuration Protocol) server.

    Security Fix(es):

    * dnsmasq: loose address/port check in reply_query() makes forging replies easier for an off-path attacker     (CVE-2020-25684)

    * dnsmasq: loose query name check in reply_query() makes forging replies easier for an off-path attacker     (CVE-2020-25685)

    * dnsmasq: multiple queries forwarded for the same name makes forging replies easier for an off-path     attacker (CVE-2020-25686)

    For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and     other related information, refer to the CVE page(s) listed in the References section.

Tenable has extracted the preceding description block directly from the Red Hat Enterprise Linux security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

ID	Name	Product	Family	Published	Updated	Severity
146242	Debian DSA-4844-1 : dnsmasq - security update	Nessus	Debian Local Security Checks	2/5/2021	1/23/2024	high
146735	EulerOS 2.0 SP3 : dnsmasq (EulerOS-SA-2021-1374)	Nessus	Huawei Local Security Checks	2/22/2021	1/19/2024	high
148050	EulerOS 2.0 SP5 : dnsmasq (EulerOS-SA-2021-1673)	Nessus	Huawei Local Security Checks	3/24/2021	1/8/2024	high
196838	RHEL 6 : dnsmasq (Unpatched Vulnerability) (deprecated)	Nessus	Red Hat Local Security Checks	5/11/2024	5/31/2024	medium
145438	Scientific Linux Security Update : dnsmasq on SL7.x x86_64 (2021:0153)	Nessus	Scientific Linux Local Security Checks	1/26/2021	12/5/2022	low
145079	RHEL 7 : dnsmasq (RHSA-2021:0154)	Nessus	Red Hat Local Security Checks	1/19/2021	11/7/2024	low
145083	RHEL 7 : dnsmasq (RHSA-2021:0156)	Nessus	Red Hat Local Security Checks	1/19/2021	11/7/2024	low

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