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Fencer Intel
medium 5.9

CVE-2020-25683 json

A flaw was found in dnsmasq before version 2.83.

published 5y ago modified 4mo ago also EUVD-2020-18345

cvss
5.9
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
88.8%
EPSS 88.8% chance of exploitation in 30 days, percentile 99.7%
public exploits
0
none known

Summary

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.

Patch / fix

  • thekelleys dnsmasq 2.83
  • dnsmasq Debian 14, Debian 13, Debian 12 2.83-1

debian advisories DEBIAN-CVE-2020-25683

  • dnsmasq Ubuntu 16.04 LTS 2.75-1ubuntu0.16.04.7
  • dnsmasq Ubuntu 18.04 LTS 2.79-1ubuntu0.2
  • dnsmasq Ubuntu 20.04 LTS 2.80-1.1ubuntu1.2

ubuntu advisories UBUNTU-CVE-2020-25683

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • dnsmasq RHEL 8 2.79-13.el8_3.1
  • dnsmasq-utils RHEL 8 2.79-13.el8_3.1
  • dnsmasq RHEL 8.1 EUS 2.79-6.el8_1.1
  • dnsmasq-utils RHEL 8.1 EUS 2.79-6.el8_1.1
  • dnsmasq RHEL 8.2 EUS 2.79-11.el8_2.2
  • dnsmasq-utils RHEL 8.2 EUS 2.79-11.el8_2.2

red hat advisories RHSA-2021:0150RHSA-2021:0152RHSA-2021:0151

  • dnsmasq SLES for SAP 12 SP5, SLES for SAP 12 SP4, SLES for SAP 12 SP3 +14 more 2.78-18.15.1
  • dnsmasq SLE Point of Sale 11 SP3 2.78-0.16.14.1
  • dnsmasq SLE Module for Basesystem 15 SP2, SLE Module for Basesystem 15 SP1 2.78-7.6.1
  • dnsmasq SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 2.78-3.11.1
  • dnsmasq SLES 11 SP4-LTSS 2.78-0.17.15.1

suse advisories SUSE-SU-2021:0166-1SUSE-SU-2021:14604-1SUSE-SU-2021:14603-1SUSE-SU-2021:0163-1SUSE-SU-2021:0162-1

  • dnsmasq openSUSE Tumbleweed 2.86-1.1
  • dnsmasq openSUSE Leap 15.1 2.78-lp151.5.6.1
  • dnsmasq openSUSE Leap 15.2 2.78-lp152.7.3.1

opensuse advisories openSUSE-SU-2024:10721-1openSUSE-SU-2021:0129-1openSUSE-SU-2021:0124-1

  • dnsmasq Alpine 3.24, Alpine 3.23, Alpine 3.22 +12 more 2.83-r0

alpine advisories ALPINE-CVE-2020-25683

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • dnsmasq Arch Linux 2.83-1

arch linux advisories AVG-1470

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2020-25683 updated cvss 5.9

dnsmasq: heap-based buffer overflow with large memcpy in get_rdata() when DNSSEC is enabled

  • Red Hat Enterprise Linux AppStream (v. 8) dnsmasq 2.79-13.el8_3.1, dnsmasq-utils 2.79-13.el8_3.1
    fixed: vendor fix “The only known way to mitigate this flaw is to disable DNSSEC altogether, by removing the `--dnssec` command line option or the `dnssec` option from dnsmasq configuration file.” RHSA-2021:0150
  • Red Hat Enterprise Linux AppStream EUS (v. 8.1) dnsmasq 2.79-6.el8_1.1, dnsmasq-utils 2.79-6.el8_1.1
    fixed: vendor fix “The only known way to mitigate this flaw is to disable DNSSEC altogether, by removing the `--dnssec` command line option or the `dnssec` option from dnsmasq configuration file.” RHSA-2021:0152
  • Red Hat Enterprise Linux AppStream EUS (v. 8.2) dnsmasq 2.79-11.el8_2.2, dnsmasq-utils 2.79-11.el8_2.2
    fixed: vendor fix “The only known way to mitigate this flaw is to disable DNSSEC altogether, by removing the `--dnssec` command line option or the `dnssec` option from dnsmasq configuration file.” RHSA-2021:0151
  • Red Hat Enterprise Linux 5 dnsmasq Red Hat Enterprise Linux 6 dnsmasq, dnsmasq-utils Red Hat Enterprise Linux 7 dnsmasq, dnsmasq-utils Red Hat Enterprise Linux 9 dnsmasq, dnsmasq-utils Red Hat OpenStack Platform 10 (Newton) dnsmasq-utils Red Hat OpenStack Platform 13 (Queens) dnsmasq-utils
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

88.78% chance of exploitation in the next 30 days, higher than 99.7% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
NVD 3.1 5.9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 7.1 AV:N/AC:M/Au:N/C:N/I:N/A:C

Affected products

  • n/a dnsmasq

Classification

Weakness
  • CWE-122 Heap-based Buffer Overflow

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.