NVD / CVE Program· CNA isc

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

HighCVSS 7.5 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 34/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 11.6% (FIRST EPSS); higher than 96.1% of all records.
Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
Fixed version: bind (Alpine:v3.10) 9.16.15-r0; bind9 (Debian:10) 1:9.11.5.P4+dfsg-5.1+deb10u5; bind9 (Debian:12) 1:9.16.15-1.
Mentioned 3 times in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to bind (Alpine:v3.10) 9.16.15-r0; bind9 (Debian:10) 1:9.11.5.P4+dfsg-5.1+deb10u5; bind9 (Debian:12) 1:9.16.15-1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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: Apr 28, 2021
Updated: Jun 16, 2026
EPSS: 11.6% · 96th percentile
CWE: CWE-617

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 30 / 40 · 7.5 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 4 / 30 · 11.6%

CNA vs NVD score

NVD: 7.5
CNA · isc: 7.5; agree

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

Not in KEV: no record of exploitation in the wild
No public exploit code on record
A fix has been released

If any of these changes, we'll tell you in the daily email digest.

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
debian	debian linux	cpe:2.3:o:debian:debian_linux
isc	bind	cpe:2.3:a:isc:bind
fedoraproject	fedora	cpe:2.3:o:fedoraproject:fedora
netapp	active iq unified manager	cpe:2.3:a:netapp:active_iq_unified_manager
netapp	cloud backup	cpe:2.3:a:netapp:cloud_backup
netapp	h300s firmware	cpe:2.3:o:netapp:h300s_firmware
netapp	h300s	cpe:2.3:h:netapp:h300s
netapp	h500s firmware	cpe:2.3:o:netapp:h500s_firmware
netapp	h500s	cpe:2.3:h:netapp:h500s
netapp	h700s firmware	cpe:2.3:o:netapp:h700s_firmware
netapp	h700s	cpe:2.3:h:netapp:h700s
netapp	h300e firmware	cpe:2.3:o:netapp:h300e_firmware

and 13 more

Versions reported by the vendor

Affected version ranges reported by the assigning authority (isc). Independent of NVD's CPE analysis and usually ahead of it.

ISC BIND9
- Open Source Branches 9.0 through 9.11 9.0.0 through versions before 9.11.30, Open Source Branches 9.12 through 9.16 9.12.0 through versions before 9.16.14, Supported Preview Branches 9.9-S through 9.11-S 9.9.3-S1 through versions before 9.11.30-S1, Supported Preview Branch 9.16-S 9.16.8-S1 through versions before 9.16.14-S1, Development Branch 9.17 9.17.0 through versiosn before 9.17.12affected

Affected versions · NVD (20)

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

debian debian linux10.0
debian debian linux9.0
fedoraproject fedora33
fedoraproject fedora34
isc bind9.12.0 and later · before 9.16.15
isc bind9.0.0 and later · before 9.11.31
isc bind9.17.0 and later · before 9.17.12
isc bind9.10.5
isc bind9.10.7
isc bind9.11.12
isc bind9.11.21
isc bind9.11.27
isc bind9.11.29
isc bind9.11.3
isc bind9.11.5
isc bind9.11.6
isc bind9.11.7
isc bind9.11.8
isc bind9.16.11
isc bind9.16.13

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
Alpine:v3.10	bind	from 9.0.0 · before 9.16.15-r0	9.16.15-r0
Debian:10	bind9	before 1:9.11.5.P4+dfsg-5.1+deb10u5	1:9.11.5.P4+dfsg-5.1+deb10u5
Debian:12	bind9	before 1:9.16.15-1	1:9.16.15-1
Debian:9	bind9	before 1:9.10.3.dfsg.P4-12.3+deb9u9	1:9.10.3.dfsg.P4-12.3+deb9u9
openSUSE:Leap 15.2	bind	before 9.16.6-lp152.14.19.1	9.16.6-lp152.14.19.1
openSUSE:Leap 15.3	bind	before 9.16.6-22.7.1	9.16.6-22.7.1
Red Hat:enterprise_linux:7::client	bind	before 32:9.11.4-26.P2.el7_9.5	32:9.11.4-26.P2.el7_9.5
Red Hat:enterprise_linux:7::client	bind-chroot	before 32:9.11.4-26.P2.el7_9.5	32:9.11.4-26.P2.el7_9.5
Red Hat:enterprise_linux:7::client	bind-debuginfo	before 32:9.11.4-26.P2.el7_9.5	32:9.11.4-26.P2.el7_9.5
Red Hat:enterprise_linux:7::client	bind-devel	before 32:9.11.4-26.P2.el7_9.5	32:9.11.4-26.P2.el7_9.5
Red Hat:enterprise_linux:7::client	bind-export-devel	before 32:9.11.4-26.P2.el7_9.5	32:9.11.4-26.P2.el7_9.5
Red Hat:enterprise_linux:7::client	bind-export-libs	before 32:9.11.4-26.P2.el7_9.5	32:9.11.4-26.P2.el7_9.5
Red Hat:enterprise_linux:7::client	bind-libs	before 32:9.11.4-26.P2.el7_9.5	32:9.11.4-26.P2.el7_9.5
Red Hat:enterprise_linux:7::client	bind-libs-lite	before 32:9.11.4-26.P2.el7_9.5	32:9.11.4-26.P2.el7_9.5
Red Hat:enterprise_linux:7::client	bind-license	before 32:9.11.4-26.P2.el7_9.5	32:9.11.4-26.P2.el7_9.5
Red Hat:enterprise_linux:7::client	bind-lite-devel	before 32:9.11.4-26.P2.el7_9.5	32:9.11.4-26.P2.el7_9.5
Red Hat:enterprise_linux:7::client	bind-pkcs11	before 32:9.11.4-26.P2.el7_9.5	32:9.11.4-26.P2.el7_9.5
Red Hat:enterprise_linux:7::client	bind-pkcs11-devel	before 32:9.11.4-26.P2.el7_9.5	32:9.11.4-26.P2.el7_9.5
Red Hat:enterprise_linux:7::client	bind-pkcs11-libs	before 32:9.11.4-26.P2.el7_9.5	32:9.11.4-26.P2.el7_9.5
Red Hat:enterprise_linux:7::client	bind-pkcs11-utils	before 32:9.11.4-26.P2.el7_9.5	32:9.11.4-26.P2.el7_9.5
Red Hat:enterprise_linux:7::client	bind-sdb	before 32:9.11.4-26.P2.el7_9.5	32:9.11.4-26.P2.el7_9.5
Red Hat:enterprise_linux:7::client	bind-sdb-chroot	before 32:9.11.4-26.P2.el7_9.5	32:9.11.4-26.P2.el7_9.5
Red Hat:enterprise_linux:7::client	bind-utils	before 32:9.11.4-26.P2.el7_9.5	32:9.11.4-26.P2.el7_9.5
Red Hat:enterprise_linux:8::appstream	bind	before 32:9.11.26-4.el8_4	32:9.11.26-4.el8_4

+96

Same product

debian: all records

Other highest-scoring records for the same primary product.

CVE-2016-9079A use-after-free vulnerability in SVG Animation has been discovered.KEV
86Now
CVE-2024-44308The issue was addressed with improved checks.KEV
68This week
CVE-2021-25216A second vulnerability in BIND's GSSAPI security policy negotiation can be targeted by a buffer overflow attack
64This week

Published before and after this one in the same product

← EarlierCVE-2019-10904Apr 6, 2019 · Roundup 1.6 allows XSS via the URI because frontends/roundup.cgi and roundup/cgi/wsgi_handler.py mishandle 404 errors.
24Monitor
← EarlierCVE-2018-5735Oct 30, 2019 · Backport of the fix for CVE-2017-3137 leads to assertion failure in validator.c:1858
30Monitor
Later →CVE-2015-1877Jun 2, 2021 · The open_generic_xdg_mime function in xdg-open in xdg-utils 1.1.0 rc1 in Debian, when using dash, does not properly handle local variables…
36Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
alpine:bind	9.16.15-r0 · Alpine:v3.10	Package registry (OSV)
debian:bind9	1:9.16.15-1 · Debian:12	Package registry (OSV)
opensuse:bind	9.16.6-lp152.14.19.1 · openSUSE:Leap 15.2	Package registry (OSV)
red hat:bind	32:9.8.2-0.68.rc1.el6_10.11 · Red Hat:rhel_els:6	Package registry (OSV)
red hat:bind-chroot	32:9.8.2-0.68.rc1.el6_10.11 · Red Hat:rhel_els:6	Package registry (OSV)
red hat:bind-debuginfo	32:9.8.2-0.68.rc1.el6_10.11 · Red Hat:rhel_els:6	Package registry (OSV)
red hat:bind-devel	32:9.8.2-0.68.rc1.el6_10.11 · Red Hat:rhel_els:6	Package registry (OSV)
red hat:bind-export-devel	32:9.11.4-26.P2.el7_9.5 · Red Hat:enterprise_linux:7::client	Package registry (OSV)
red hat:bind-export-libs	32:9.11.4-26.P2.el7_9.5 · Red Hat:enterprise_linux:7::client	Package registry (OSV)
red hat:bind-libs	32:9.8.2-0.68.rc1.el6_10.11 · Red Hat:rhel_els:6	Package registry (OSV)
red hat:bind-libs-lite	32:9.11.4-26.P2.el7_9.5 · Red Hat:enterprise_linux:7::client	Package registry (OSV)
red hat:bind-license	32:9.11.4-26.P2.el7_9.5 · Red Hat:enterprise_linux:7::client	Package registry (OSV)
red hat:bind-lite-devel	32:9.11.4-26.P2.el7_9.5 · Red Hat:enterprise_linux:7::client	Package registry (OSV)
red hat:bind-sdb	32:9.8.2-0.68.rc1.el6_10.11 · Red Hat:rhel_els:6	Package registry (OSV)
red hat:bind-utils	32:9.8.2-0.68.rc1.el6_10.11 · Red Hat:rhel_els:6	Package registry (OSV)
rocky linux:bind	2:9.11.26-4.el8_4 · Rocky Linux:8	Package registry (OSV)
suse:bind	9.11.22-3.34.1 · SUSE:OpenStack Cloud 9	Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.