CVE-2021-25214Network attack vector

Service crash via malformed IXFR SOA records

Published Apr 29, 2021 · Updated Sep 17, 2024

Reachable assertion in Internet Systems Consortium BIND 9 allows remote authenticated users to crash named via a malformed IXFR stream. An IXFR stream whose SOA record owner is not the zone apex makes named remove the zone SOA from its database, so the next SOA refresh hits an assertion and terminates the process. The attacker must be a server permitted to supply zone transfers; the bounded consequence is interruption of the DNS service process.

CVSS severity6.5
Medium
EPSS probability5.99%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Reachable assertion in Internet Systems Consortium BIND 9 allows remote authenticated users to crash named via a malformed IXFR stream. An IXFR stream whose SOA record owner is not the zone apex makes named remove the zone SOA from its database, so the next SOA refresh hits an assertion and terminates the process. The attacker must be a server permitted to supply zone transfers; the bounded consequence is interruption of the DNS service process.

The record

CVE
CVE-2021-25214
Published
Apr 29, 2021
Updated
Sep 17, 2024
Vendor
Internet Systems Consortium
Product
BIND 9
Classifications
CWE-617, T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 29, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 17, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=Development Branch 9.17 9.17.0 through versiosn before 9.17.12
  2. Affected versionversion=Open Source Branch 9.8 9.8.5 through 9.8.8
  3. Affected versionversion=Open Source Branches 9.12 through 9.16 9.12.0 through versions before 9.16.14
  4. Affected versionversion=Open Source Branches 9.9 through 9.11 9.9.3 through versions before 9.11.30
  5. Affected versionversion=Supported Preview Branch 9.16-S 9.16.8-S1 through versions before 9.16.14-S1
  6. Affected versionversion=Supported Preview Branches 9.9-S through 9.11-S 9.9.3-S1 through versions before 9.11.30-S1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Internet Systems Consortium · BIND 9version=Development Branch 9.17 9.17.0 through versiosn before 9.17.12; version=Open Source Branch 9.8 9.8.5 through 9.8.8; version=Open Source Branches 9.12 through 9.16 9.12.0 through versions before 9.16.14; version=Open Source Branches 9.9 through 9.11 9.9.3 through versions before 9.11.30; version=Supported Preview Branch 9.16-S 9.16.8-S1 through versions before 9.16.14-S1; version=Supported Preview Branches 9.9-S through 9.11-S 9.9.3-S1 through versions before 9.11.30-S1

Published CVSS scores

6.5Internet Systems ConsortiumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
4.0NIST National Vulnerability DatabaseAV:N/AC:L/Au:S/C:N/I:N/A:P

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-617Reachable Assertion
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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