CVE-2020-25683 [Medium] | Denial of Service in Dnsmasq

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.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-06-28	86.16%	86.04%	-0.12%
2	2026-06-15	31.32%	86.16%	+54.84%
3	2025-12-28	—	31.32%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-06-28

86.16%

86.04%

-0.12%

2026-06-15

31.32%

86.16%

+54.84%

2025-12-28

—

31.32%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
5.9	3.1	MEDIUM	`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H` 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:N) Data isn’t meaningfully altered or forged. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	2.2	3.6	[email protected]
7.1	2.0	HIGH	`AV:N/AC:M/Au:N/C:N/I:N/A:C` 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:N) No integrity impact. Availability impact (A:C) Complete availability impact.	8.6	6.9	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

5.9

3.1

MEDIUM

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H 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:N): Data isn’t meaningfully altered or forged.
Availability (A:H): Could take the service down hard or make it unusable for people who depend on it.

2.2

3.6

[email protected]

7.1

2.0

HIGH

AV:N/AC:M/Au:N/C:N/I:N/A:C 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:N): No integrity impact.
Availability impact (A:C): Complete availability impact.

8.6

6.9

[email protected]

OS Trackers for CVE-2020-25683

vendor	priority	summary	link
`alpine`	—	CVE-2020-25683: 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-2020-25683
`debian`	not yet assigned	CVE-2020-25683 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-2020-25683
`gentoo`	normal	CVE-2020-25683: 1 GLSA(s) (202101-17), 1 atom(s) (net-dns/dnsmasq); latest impact normal.	https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2020-25683
`redhat`	medium	—	https://access.redhat.com/security/cve/CVE-2020-25683
`suse`	high	CVE-2020-25683 severity important: SUSE including 25 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, …), 64 product×package rows across 53 product lines (Container suse/sles/15.2/virt-launcher, Container suse/sles/15.3/virt-launcher, … (53 product lines)): Fixed 64.	https://www.suse.com/security/cve/CVE-2020-25683/
`ubuntu`	medium	CVE-2020-25683 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-2020-25683

Affected software / configurations for CVE-2020-25683

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	9.0	cpe:2.3:o:debian:debian_linux:9.0:::::::*
debian	debian_linux	10.0	cpe:2.3:o:debian:debian_linux:10.0:::::::*

References for CVE-2020-25683

URL	Tags
https://bugzilla.redhat.com/show_bug.cgi?id=1882018	Issue Tracking Patch Third Party Advisory
https://lists.debian.org/debian-lts-announce/2021/03/msg00027.html	Mailing List 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.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-2020-25683

Exploit prediction scoring system (EPSS) score for CVE-2020-25683

Common vulnerability scoring system (CVSS) metrics for CVE-2020-25683

Weakness enumeration for CVE-2020-25683

OS Trackers for CVE-2020-25683

Affected software / configurations for CVE-2020-25683

References for CVE-2020-25683