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

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.

Published: 2021-04-29 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-25215 is rated High Risk (68.4/100): CVSS High severity, with high exploitation likelihood (EPSS 11.39%, 95th percentile). EPSS ranks this CVE among the most likely to be exploited in the near term. EPSS rose +9.14% over the last day, indicating growing attacker interest. High exploitation likelihood—assess exposure and prioritize remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-25215

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 2.25% 11.39% +9.14%
2 2026-06-08 2.02% 2.25% +0.24%
3 2026-06-07 — 2.02% —

Full EPSS history (46 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-25215

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
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:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 [email protected]
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
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:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 [email protected]
5.0 2.0 MEDIUM
AV:N/AC:L/Au:N/C:N/I:N/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:P)
Partial availability impact.
 10.0 2.9 [email protected]

Weakness enumeration for CVE-2021-25215

OS Trackers for CVE-2021-25215

vendor priority summary link
alpine high CVE-2021-25215: 1 source package rows (bind); 10 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 0. https://security.alpinelinux.org/vuln/CVE-2021-25215
debian not yet assigned CVE-2021-25215 not yet assigned priority: Debian including 1 source packages (bind9), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2021-25215
redhat high — https://access.redhat.com/security/cve/CVE-2021-25215
suse high CVE-2021-25215 severity important: SUSE including 379 source package names (amazon/suse-sles-15-sp1-chost-byos-v20210304-hvm-ssd-x86_64, amazon/suse-sles-15-sp1-chost-byos-v20220127-hvm-ssd-x86_64, …), 1261 product×package rows across 109 product lines (HPE Helion OpenStack 8, Image SLES12-SP5-Azure-BYOS, … (109 product lines)): Fixed 1122, Known Affected 137, Known Not Affected 2. https://www.suse.com/security/cve/CVE-2021-25215/
ubuntu medium CVE-2021-25215 medium priority: Ubuntu including 1 source packages (bind9), 15 status rows across 15 suites (bionic, focal, groovy, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, trusty, upstream, xenial): released 15. https://ubuntu.com/security/CVE-2021-25215

Affected software / configurations for CVE-2021-25215

Vendor Product Version Raw CPE
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:*:*:*:*:*:*:*
isc bind >= 9.0.0, < 9.11.31 cpe:2.3:a:isc:bind:*:*:*:*:-:*:*:*
isc bind >= 9.12.0, < 9.16.15 cpe:2.3:a:isc:bind:*:*:*:*:-:*:*:*
isc bind >= 9.17.0, < 9.17.12 cpe:2.3:a:isc:bind:*:*:*:*:-:*:*:*
isc bind 9.9.3 cpe:2.3:a:isc:bind:9.9.3:s1:*:*:supported_preview:*:*:*
isc bind 9.9.12 cpe:2.3:a:isc:bind:9.9.12:s1:*:*:supported_preview:*:*:*
isc bind 9.9.13 cpe:2.3:a:isc:bind:9.9.13:s1:*:*:supported_preview:*:*:*
isc bind 9.10.5 cpe:2.3:a:isc:bind:9.10.5:s1:*:*:supported_preview:*:*:*
isc bind 9.10.7 cpe:2.3:a:isc:bind:9.10.7:s1:*:*:supported_preview:*:*:*
isc bind 9.11.3 cpe:2.3:a:isc:bind:9.11.3:s1:*:*:supported_preview:*:*:*
isc bind 9.11.5 cpe:2.3:a:isc:bind:9.11.5:s3:*:*:supported_preview:*:*:*
isc bind 9.11.5 cpe:2.3:a:isc:bind:9.11.5:s5:*:*:supported_preview:*:*:*
isc bind 9.11.5 cpe:2.3:a:isc:bind:9.11.5:s6:*:*:supported_preview:*:*:*
isc bind 9.11.6 cpe:2.3:a:isc:bind:9.11.6:s1:*:*:supported_preview:*:*:*
isc bind 9.11.7 cpe:2.3:a:isc:bind:9.11.7:s1:*:*:supported_preview:*:*:*
isc bind 9.11.8 cpe:2.3:a:isc:bind:9.11.8:s1:*:*:supported_preview:*:*:*
isc bind 9.11.12 cpe:2.3:a:isc:bind:9.11.12:s1:*:*:supported_preview:*:*:*
isc bind 9.11.21 cpe:2.3:a:isc:bind:9.11.21:s1:*:*:supported_preview:*:*:*
isc bind 9.11.27 cpe:2.3:a:isc:bind:9.11.27:s1:*:*:supported_preview:*:*:*
isc bind 9.11.29 cpe:2.3:a:isc:bind:9.11.29:s1:*:*:supported_preview:*:*:*
isc bind 9.16.8 cpe:2.3:a:isc:bind:9.16.8:s1:*:*:supported_preview:*:*:*
isc bind 9.16.11 cpe:2.3:a:isc:bind:9.16.11:s1:*:*:supported_preview:*:*:*
isc bind 9.16.13 cpe:2.3:a:isc:bind:9.16.13:s1:*:*:supported_preview:*:*:*
fedoraproject fedora 33 cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*
fedoraproject fedora 34 cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*
netapp active_iq_unified_manager — cpe:2.3:a:netapp:active_iq_unified_manager:-:*:*:*:*:vmware_vsphere:*:*
netapp cloud_backup — cpe:2.3:a:netapp:cloud_backup:-:*:*:*:*:*:*:*
netapp h300s_firmware — cpe:2.3:o:netapp:h300s_firmware:-:*:*:*:*:*:*:*
netapp h500s_firmware — cpe:2.3:o:netapp:h500s_firmware:-:*:*:*:*:*:*:*
netapp h700s_firmware — cpe:2.3:o:netapp:h700s_firmware:-:*:*:*:*:*:*:*
netapp h300e_firmware — cpe:2.3:o:netapp:h300e_firmware:-:*:*:*:*:*:*:*
netapp h500e_firmware — cpe:2.3:o:netapp:h500e_firmware:-:*:*:*:*:*:*:*
netapp h700e_firmware — cpe:2.3:o:netapp:h700e_firmware:-:*:*:*:*:*:*:*
netapp h410s_firmware — cpe:2.3:o:netapp:h410s_firmware:-:*:*:*:*:*:*:*
netapp a250_firmware — cpe:2.3:o:netapp:a250_firmware:-:*:*:*:*:*:*:*
netapp 500f_firmware — cpe:2.3:o:netapp:500f_firmware:-:*:*:*:*:*:*:*
oracle tekelec_platform_distribution >= 7.4.0, <= 7.7.1 cpe:2.3:a:oracle:tekelec_platform_distribution:*:*:*:*:*:*:*:*
siemens sinec_infrastructure_network_services < 1.0.1.1 cpe:2.3:a:siemens:sinec_infrastructure_network_services:*:*:*:*:*:*:*:*

References for CVE-2021-25215

URL Tags
http://www.openwall.com/lists/oss-security/2021/04/29/1 Mailing List Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/04/29/2 Mailing List Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/04/29/3 Mailing List Third Party Advisory
http://www.openwall.com/lists/oss-security/2021/04/29/4 Mailing List Third Party Advisory
https://cert-portal.siemens.com/productcert/pdf/ssa-389290.pdf Patch Third Party Advisory
https://kb.isc.org/v1/docs/cve-2021-25215 Vendor Advisory
https://lists.debian.org/debian-lts-announce/2021/05/msg00001.html Mailing List Third Party Advisory
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/ Third Party Advisory
https://www.debian.org/security/2021/dsa-4909 Third Party Advisory
https://www.oracle.com/security-alerts/cpuoct2021.html Patch Third Party Advisory
cvelogic Threat Intelligence