CVE-2021-25218

A too-strict assertion check could be triggered when responses in BIND 9.16.19 and 9.17.16 require UDP fragmentation if RRL is in use

7.5 HighFix available

In BIND 9.16.19, 9.17.16. Also, version 9.16.19-S1 of BIND Supported Preview Edition When a vulnerable version of named receives a query under the circumstances described above, the named process will terminate due to a failed assertion check. The vulnerability affects only BIND 9 releases 9.16.19, 9.17.16, and release 9.16.19-S1 of the BIND Supported Preview Edition.

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: None

What an attacker can affect

Confidentiality: None
Integrity: None
Availability: High

Exploit likelihood

3.66%Up 3.0 points since Aug 19, 2021

What each source reports

CVE List Score used 7.5

A too-strict assertion check could be triggered when responses in BIND 9.16.19 and 9.17.16 require UDP fragmentation if RRL is in use

Record: CVE-2021-25218
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

EUVDEUVD-2021-12129 7.5

Record: EUVD-2021-12129
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-03

GitHub AdvisoriesGHSA-cc8x-chx9-c63q No score

In BIND 9.16.19, 9.17.16. Also, version 9.16.19-S1 of BIND Supported Preview Edition When a...

Record: GHSA-cc8x-chx9-c63q
Weakness: CWE-617
Updated: 2026-11-02

NVD 7.5

Record: CVE-2021-25218
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS 2.0: 5.0 MediumAV:N/AC:L/Au:N/C:N/I:N/A:P
Weakness: CWE-617
Updated: 2026-11-02

OSVALPINE-CVE-2021-25218 7.5

Record: ALPINE-CVE-2021-25218
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

OSVBELL-CVE-2021-25218 7.5

CVE-2021-25218 does not affect BellSoft software

Record: BELL-CVE-2021-25218
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

OSV 7.5

Record: CVE-2021-25218
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

OSVopenSUSE-SU-2024:10650-1 No score

bind-9.16.20-1.4 on GA media

These are all security issues fixed in the bind-9.16.20-1.4 package on the GA media of openSUSE Tumbleweed.

Record: openSUSE-SU-2024:10650-1
Updated: 2026-11-02

Affected products

Affected packages

Affected packages
Package	Affected	Fixed
`bind` Alpine:v3.11	before 9.16.20-r0	9.16.20-r0
`bind` Alpine:v3.12	before 9.16.20-r0	9.16.20-r0
`bind` Alpine:v3.13	before 9.16.20-r0	9.16.20-r0
`bind` Alpine:v3.14	before 9.16.20-r0	9.16.20-r0
`bind` Alpine:v3.15	before 9.16.20-r0	9.16.20-r0
`bind` Alpine:v3.16	before 9.16.20-r0	9.16.20-r0
`bind` Alpine:v3.17	before 9.16.20-r0	9.16.20-r0
`bind` Alpine:v3.18	before 9.16.20-r0	9.16.20-r0
`bind` Alpine:v3.19	before 9.16.20-r0	9.16.20-r0
`bind` Alpine:v3.20	before 9.16.20-r0	9.16.20-r0

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Affected packages
Package	Affected	Fixed
`bind` Alpine:v3.21	before 9.16.20-r0	9.16.20-r0
`bind` Alpine:v3.22	before 9.16.20-r0	9.16.20-r0
`bind` Alpine:v3.23	before 9.16.20-r0	9.16.20-r0
`bind` Alpine:v3.24	before 9.16.20-r0	9.16.20-r0
`bind` openSUSE:Tumbleweed	before 9.16.20-1.4	9.16.20-1.4

History

History
Recorded	Changed	Sources
Nov 3, 2026	aliases, published	EUVD
Nov 2, 2026	first indexed	CVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-25218 is a high vulnerability (CVSS 7.5) in Isc Bind, published August 18, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 3.66%, the 89th percentile. Fixed in bind 9.16.20-r0.

References

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