CVE-2020-25685 [Low] | Security Vulnerability in Dnsmasq

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.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-05-28	0.32%	0.42%	+0.11%
2	2026-03-26	0.36%	0.32%	-0.04%
3	2026-01-16	—	0.36%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-05-28

0.32%

0.42%

+0.11%

2026-03-26

0.36%

0.32%

-0.04%

2026-01-16

—

0.36%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
3.7	3.1	LOW	`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. Attack complexity (AC:H) Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work. Privileges required (PR:N) No account or special rights needed—anonymous or random user is enough. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:N) Doesn’t really leak secrets in a meaningful way. Integrity (I:L) Attackers could change some data, but it’s limited—not everything goes. Availability (A:N) Service keeps running; no real outage angle.	2.2	1.4	[email protected]
4.3	2.0	MEDIUM	`AV:N/AC:M/Au:N/C:N/I:P/A:N` Click to expand Access vector (AV:N) Can be exploited remotely over network reachability. Access complexity (AC:M) Exploitation needs some favorable conditions, but not exceptional ones. Authentication (AU:N) No authentication is required. Confidentiality impact (C:N) No confidentiality impact. Integrity impact (I:P) Partial integrity impact. Availability impact (A:N) No availability impact.	8.6	2.9	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

3.7

3.1

LOW

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N Click to expand

Attack vector (AV:N): Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H): Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:N): No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N): Doesn’t really leak secrets in a meaningful way.
Integrity (I:L): Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N): Service keeps running; no real outage angle.

2.2

1.4

[email protected]

4.3

2.0

MEDIUM

AV:N/AC:M/Au:N/C:N/I:P/A:N Click to expand

Access vector (AV:N): Can be exploited remotely over network reachability.
Access complexity (AC:M): Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N): No authentication is required.
Confidentiality impact (C:N): No confidentiality impact.
Integrity impact (I:P): Partial integrity impact.
Availability impact (A:N): No availability impact.

8.6

2.9

[email protected]

OS Trackers for CVE-2020-25685

vendor	priority	summary	link
`alpine`	—	CVE-2020-25685: 1 source package rows (dnsmasq); 25 state rows across 10 repos (3.10-main, 3.11-main, 3.12-main, 3.17-main, 3.18-main, 3.19-main, 3.20-main, 3.21-main, 3.22-main, edge-main); fixed 10, open 15.	https://security.alpinelinux.org/vuln/CVE-2020-25685
`debian`	not yet assigned	CVE-2020-25685 not yet assigned priority: Debian including 1 source packages (dnsmasq), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5.	https://security-tracker.debian.org/tracker/CVE-2020-25685
`gentoo`	normal	CVE-2020-25685: 1 GLSA(s) (202101-17), 1 atom(s) (net-dns/dnsmasq); latest impact normal.	https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2020-25685
`redhat`	medium	—	https://access.redhat.com/security/cve/CVE-2020-25685
`suse`	high	CVE-2020-25685 severity important: SUSE including 27 source package names (0.38.1.5.8.40:dnsmasq-2.78-7.6.1, 0.45.0.8.14.1:dnsmasq-2.78-7.6.1, …), 66 product×package rows across 54 product lines (Container suse/sles/15.2/virt-launcher, Container suse/sles/15.3/virt-launcher, … (54 product lines)): Fixed 66.	https://www.suse.com/security/cve/CVE-2020-25685/
`ubuntu`	medium	CVE-2020-25685 medium priority: Ubuntu including 1 source packages (dnsmasq), 15 status rows across 15 suites (bionic, focal, groovy, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, trusty, upstream, xenial): released 14, ignored 1.	https://ubuntu.com/security/CVE-2020-25685

Affected software / configurations for CVE-2020-25685

Vendor	Product	Version	Raw CPE
thekelleys	dnsmasq	< 2.83	cpe:2.3:a:thekelleys:dnsmasq::::::::
fedoraproject	fedora	32	cpe:2.3:o:fedoraproject:fedora:32:::::::*
fedoraproject	fedora	33	cpe:2.3:o:fedoraproject:fedora:33:::::::*
debian	debian_linux	10.0	cpe:2.3:o:debian:debian_linux:10.0:::::::*
arista	eos	>= 4.21, < 4.21.14m	cpe:2.3:o:arista:eos::::::::
arista	eos	>= 4.22, < 4.22.9m	cpe:2.3:o:arista:eos::::::::
arista	eos	>= 4.23, < 4.23.7m	cpe:2.3:o:arista:eos::::::::
arista	eos	>= 4.24, < 4.24.5m	cpe:2.3:o:arista:eos::::::::
arista	eos	>= 4.25, < 4.25.2f	cpe:2.3:o:arista:eos::::::::

References for CVE-2020-25685

URL	Tags
https://bugzilla.redhat.com/show_bug.cgi?id=1889688	Issue Tracking Patch Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QGB7HL3OWHTLEPSMLDGOMXQKG3KM2QME/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WYW3IR6APUSKOYKL5FT3ACTIHWHGQY32/
https://security.gentoo.org/glsa/202101-17	Third Party Advisory
https://www.arista.com/en/support/advisories-notices/security-advisories/12135-security-advisory-61	Third Party Advisory
https://www.debian.org/security/2021/dsa-4844	Third Party Advisory
https://www.jsof-tech.com/disclosures/dnspooq/	Third Party Advisory
https://www.kb.cert.org/vuls/id/434904

URL

CVE-2020-25685

Exploit prediction scoring system (EPSS) score for CVE-2020-25685

Common vulnerability scoring system (CVSS) metrics for CVE-2020-25685

Weakness enumeration for CVE-2020-25685

OS Trackers for CVE-2020-25685

Affected software / configurations for CVE-2020-25685

References for CVE-2020-25685