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

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 3.6% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2021-08-18 · updated 2026-06-17
Weakness: CWE-617

Description

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.

Affected products

Fedoraproject Fedora: 34
ISC BIND: 9.16.19, 9.17.16, 9.17.16-s1

References

http://www.openwall.com/lists/oss-security/2021/08/18/3
http://www.openwall.com/lists/oss-security/2021/08/20/2
https://kb.isc.org/v1/docs/cve-2021-25218
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZPJCLGSR4BTGFLBLGIE5TEQP2SNJKGVL/
https://security.netapp.com/advisory/ntap-20210909-0002/
http://www.openwall.com/lists/oss-security/2021/08/18/3
http://www.openwall.com/lists/oss-security/2021/08/20/2
https://kb.isc.org/v1/docs/cve-2021-25218
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZPJCLGSR4BTGFLBLGIE5TEQP2SNJKGVL/
https://security.netapp.com/advisory/ntap-20210909-0002/

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