CVE-2020-25682 [High] | Memory Corruption in Dnsmasq

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.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2025-12-28	40.52%	34.29%	-6.23%
2	2025-12-27	34.29%	40.52%	+6.23%
3	2025-11-21	—	34.29%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2025-12-28

40.52%

34.29%

-6.23%

2025-12-27

34.29%

40.52%

+6.23%

2025-11-21

—

34.29%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
8.1	3.1	HIGH	`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/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:H) Serious risk that confidential data gets exposed in a big way. Integrity (I:H) They could widely tamper with or forge data—trust in the data is badly hurt. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	2.2	5.9	[email protected]
8.3	2.0	HIGH	`AV:N/AC:M/Au:N/C:P/I:P/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:P) Partial confidentiality impact. Integrity impact (I:P) Partial integrity impact. Availability impact (A:C) Complete availability impact.	8.6	8.5	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

8.1

3.1

HIGH

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/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:H): Serious risk that confidential data gets exposed in a big way.
Integrity (I:H): They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H): Could take the service down hard or make it unusable for people who depend on it.

2.2

5.9

[email protected]

8.3

2.0

HIGH

AV:N/AC:M/Au:N/C:P/I:P/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:P): Partial confidentiality impact.
Integrity impact (I:P): Partial integrity impact.
Availability impact (A:C): Complete availability impact.

8.6

8.5

[email protected]

OS Trackers for CVE-2020-25682

vendor	priority	summary	link
`alpine`	—	CVE-2020-25682: 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-2020-25682
`debian`	not yet assigned	CVE-2020-25682 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-2020-25682
`gentoo`	normal	CVE-2020-25682: 1 GLSA(s) (202101-17), 1 atom(s) (net-dns/dnsmasq); latest impact normal.	https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2020-25682
`redhat`	high	—	https://access.redhat.com/security/cve/CVE-2020-25682
`suse`	high	CVE-2020-25682 severity important: SUSE including 23 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, …), 62 product×package rows across 52 product lines (Container suse/sles/15.2/virt-launcher, Container suse/sles/15.3/virt-launcher, … (52 product lines)): Fixed 62.	https://www.suse.com/security/cve/CVE-2020-25682/
`ubuntu`	medium	CVE-2020-25682 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, not-affected 1.	https://ubuntu.com/security/CVE-2020-25682

Affected software / configurations for CVE-2020-25682

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-2020-25682

URL	Tags
https://bugzilla.redhat.com/show_bug.cgi?id=1882014	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-2020-25682

Exploit prediction scoring system (EPSS) score for CVE-2020-25682

Common vulnerability scoring system (CVSS) metrics for CVE-2020-25682

Weakness enumeration for CVE-2020-25682

OS Trackers for CVE-2020-25682

Affected software / configurations for CVE-2020-25682

References for CVE-2020-25682