What’s Vulnerable › Vulnerabilities

CVE-2021-25215: An assertion check can fail while answering queries for DNAME records that require the DNAME to be processed to resolve itself

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 11.8% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-04-29 · updated 2026-06-17
• Weakness: CWE-617

Description

In BIND 9.0.0 -> 9.11.29, 9.12.0 -> 9.16.13, and versions BIND 9.9.3-S1 -> 9.11.29-S1 and 9.16.8-S1 -> 9.16.13-S1 of BIND Supported Preview Edition, as well as release versions 9.17.0 -> 9.17.11 of the BIND 9.17 development branch, when a vulnerable version of named receives a query for a record triggering the flaw described above, the named process will terminate due to a failed assertion check. The vulnerability affects all currently maintained BIND 9 branches (9.11, 9.11-S, 9.16, 9.16-S, 9.17) as well as all other versions of BIND 9.

Affected products

• Debian Linux: 9.0, 10.0
• Fedoraproject Fedora: 33, 34
• ISC BIND: from 9.0.0 before 9.11.31; from 9.12.0 before 9.16.15; from 9.17.0 before 9.17.12; 9.9.3-s1, 9.9.12-s1, 9.9.13-s1, 9.10.5-s1, 9.10.7-s1, 9.11.3-s1 (+13) — fixed in 9.11.31, 9.16.15, 9.17.12
• NetApp 500F Firmware: all versions
• NetApp A250 Firmware: all versions
• Active IQ Unified Manager for VMware vSphere, Linux, and Microsoft Windows: all versions
• NetApp Cloud Backup: all versions
• NetApp H300E Firmware: all versions
• NetApp H300S Firmware: all versions
• NetApp H410S Firmware: all versions
• NetApp H500E Firmware: all versions
• NetApp H500S Firmware: all versions
• NetApp H700E Firmware: all versions
• NetApp H700S Firmware: all versions
• Oracle Tekelec Platform Distribution: from 7.4.0 through 7.7.1
• Siemens Sinec Infrastructure Network Services: before 1.0.1.1 — fixed in 1.0.1.1

How to fix

Upgrade to a fixed version: ISC BIND 9.11.31, 9.16.15, 9.17.12; Siemens Sinec Infrastructure Network Services 1.0.1.1. Check the vendor advisory for mitigations.

References

• http://www.openwall.com/lists/oss-security/2021/04/29/1
• http://www.openwall.com/lists/oss-security/2021/04/29/2
• http://www.openwall.com/lists/oss-security/2021/04/29/3
• http://www.openwall.com/lists/oss-security/2021/04/29/4
• https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf
• https://kb.isc.org/v1/docs/cve-2021-25215
• https://lists.debian.org/debian-lts-announce/2021/05/msg00001.html
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VEC2XG4Q2ODTN2C4CGXEIXU3EUTBMK7L/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZDSRPCJQ7MZC6CENH5PO3VQOFI7VSWBE/
• https://security.netapp.com/advisory/ntap-20210521-0006/
• https://www.debian.org/security/2021/dsa-4909
• https://www.oracle.com/security-alerts/cpuoct2021.html

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