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CVE-2021-25215

29
FAUCET Score

CVE-2021-25215 is a denial-of-service vulnerability affecting multiple versions of BIND 9, including those from ISC, Debian, Fedora, NetApp, Oracle, and Siemens. An unauthenticated attacker can remotely trigger a failed assertion check in the named process by sending a specially crafted query, causing the DNS server to terminate. This vulnerability has a CVSS score of 7.5 (High) due to its remote attack vector, low attack complexity, and high impact on availability. While there is no known active exploitation or public exploit code, the vulnerability has garnered some community discussion and media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
9.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
10.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
>= 9.0.0, < 9.11.31CPE matchmatch criteria
cpe:2.3:a:isc:bind:*:*:*:*:-:*:*:*
>= 9.12.0, < 9.16.15CPE matchmatch criteria
cpe:2.3:a:isc:bind:*:*:*:*:-:*:*:*
>= 9.17.0, < 9.17.12CPE matchmatch criteria
cpe:2.3:a:isc:bind:*:*:*:*:-:*:*:*

CVSS Data

CVSS version used by this source: 3.1

7.5HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
11.39%
Probability of exploitation in next 30 days
EPSS Percentile
95.5%
Percentile rank of EPSS score among Peer Group
As of 2026-07-26
Model: v2026.06.15
This CVE's current EPSS score of 0.1139 is in the 93rd percentile among its peer group of 51,485 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (17)

microsoftpatch availablevia msrc
Product: cm1 bind 9.16.15-1 on CBL Mariner 1.0Fixed in: 9.16.15-1
microsoftpatch availablevia msrc
Product: 17071-16820Fixed in: 9.16.15-1
microsoftpatch availablevia msrc
Product: CBL Mariner 1.0 ARMFixed in: 9.16.15-1
microsoftpatch availablevia msrc
Product: CBL Mariner 1.0 x64Fixed in: 9.16.15-1
oraclepatch availablevia nvd_reference
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 7.2 Advanced Update SupportFixed in: bind-32:9.9.4-29.el7_2.11
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 7.3 Advanced Update SupportFixed in: bind-32:9.9.4-50.el7_3.6
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 7.4 Advanced Update SupportFixed in: bind-32:9.9.4-51.el7_4.6
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 7.4 Telco Extended Update SupportFixed in: bind-32:9.9.4-51.el7_4.6
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 7.4 Update Services for SAP SolutionsFixed in: bind-32:9.9.4-51.el7_4.6
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 7.7 Extended Update SupportFixed in: bind-32:9.11.4-9.P2.el7_7.5
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: bind-32:9.11.26-4.el8_4
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.1 Extended Update SupportFixed in: bind-32:9.11.4-26.P2.el8_1.5
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.2 Extended Update SupportFixed in: bind-32:9.11.13-6.el8_2.3
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 7Fixed in: bind-32:9.11.4-26.P2.el7_9.5
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 6 Extended Lifecycle SupportFixed in: bind-32:9.8.2-0.68.rc1.el6_10.11
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 7.6 Extended Update SupportFixed in: bind-32:9.9.4-74.el7_6.7
View patch

Vendor Advisories (3)

microsoft2021-May/CVE-2021-25215

CVE-2021-25215

May 11, 2021
redhatCVE-2021-25215Important

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

Apr 28, 2021
microsoft2021-Apr/CVE-2021-25215Important

An assertion check can fail while answering queries for DNAME records that require the DNAME to be processed to resolve itself

Apr 13, 2021

References

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