How severe is CVE-2021-25219?

CVE-2021-25219 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.

Is CVE-2021-25219 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 8% (94th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-25219?

CVE-2021-25219 primarily affects Isc Bind. In total, 41 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-25219?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-25219 published?

CVE-2021-25219 was published on 2021-10-27 and last updated on 2026-06-17.

CVE-2021-25219

CVE-2021-25219 is a medium-severity vulnerability in Isc Bind with a CVSS 3.x base score of 5.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low.

Key facts

Severity: Medium (CVSS 3.x base score 5.3)
CVSS v2: 5.0
EPSS exploit prediction: 8% (94th percentile)
Actively exploited: Not listed in CISA KEV
Affected product: Isc Bind
Published: 2021-10-27
Last modified: 2026-06-17

Description

In BIND 9.3.0 -> 9.11.35, 9.12.0 -> 9.16.21, and versions 9.9.3-S1 -> 9.11.35-S1 and 9.16.8-S1 -> 9.16.21-S1 of BIND Supported Preview Edition, as well as release versions 9.17.0 -> 9.17.18 of the BIND 9.17 development branch, exploitation of broken authoritative servers using a flaw in response processing can cause degradation in BIND resolver performance. The way the lame cache is currently designed makes it possible for its internal data structures to grow almost infinitely, which may cause significant delays in client query processing.

Frequently asked questions

What is CVE-2021-25219?: In BIND 9.3.0 -> 9.11.35, 9.12.0 -> 9.16.21, and versions 9.9.3-S1 -> 9.11.35-S1 and 9.16.8-S1 -> 9.16.21-S1 of BIND Supported Preview Edition, as well as release versions 9.17.0 -> 9.17.18 of the BIND 9.17 development branch, exploitation of broken authoritative servers using a flaw in response processing can cause degradation in BIND resolver performance. The way the lame cache is currently designed makes it possible for its internal data structures to grow almost infinitely, which may cause significant delays in client query processing.
How severe is CVE-2021-25219?: CVE-2021-25219 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.
Is CVE-2021-25219 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 8% (94th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-25219?: CVE-2021-25219 primarily affects Isc Bind. In total, 41 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-25219?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-25219 published?: CVE-2021-25219 was published on 2021-10-27 and last updated on 2026-06-17.

References

Affected products (41)

cpe:2.3:a:isc:bind:*:*:*:*:-:*:*:*
cpe:2.3:a:isc:bind:9.9.3:s1:*:*:supported_preview:*:*:*
cpe:2.3:a:isc:bind:9.9.12:s1:*:*:supported_preview:*:*:*
cpe:2.3:a:isc:bind:9.9.13:s1:*:*:supported_preview:*:*:*
cpe:2.3:a:isc:bind:9.10.5:s1:*:*:supported_preview:*:*:*
cpe:2.3:a:isc:bind:9.10.7:s1:*:*:supported_preview:*:*:*
cpe:2.3:a:isc:bind:9.11.3:s1:*:*:supported_preview:*:*:*
cpe:2.3:a:isc:bind:9.11.5:s3:*:*:supported_preview:*:*:*
cpe:2.3:a:isc:bind:9.11.5:s5:*:*:supported_preview:*:*:*
cpe:2.3:a:isc:bind:9.11.5:s6:*:*:supported_preview:*:*:*
cpe:2.3:a:isc:bind:9.11.6:s1:*:*:supported_preview:*:*:*
cpe:2.3:a:isc:bind:9.11.7:s1:*:*:supported_preview:*:*:*
cpe:2.3:a:isc:bind:9.11.8:s1:*:*:supported_preview:*:*:*
cpe:2.3:a:isc:bind:9.11.12:s1:*:*:supported_preview:*:*:*
cpe:2.3:a:isc:bind:9.11.21:s1:*:*:supported_preview:*:*:*
cpe:2.3:a:isc:bind:9.11.27:s1:*:*:supported_preview:*:*:*
cpe:2.3:a:isc:bind:9.11.29:s1:*:*:supported_preview:*:*:*
cpe:2.3:a:isc:bind:9.11.35:s1:*:*:supported_preview:*:*:*
cpe:2.3:a:isc:bind:9.16.8:s1:*:*:supported_preview:*:*:*
cpe:2.3:a:isc:bind:9.16.11:s1:*:*:supported_preview:*:*:*
cpe:2.3:a:isc:bind:9.16.13:s1:*:*:supported_preview:*:*:*
cpe:2.3:a:isc:bind:9.16.21:s1:*:*:supported_preview:*:*:*
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*
cpe:2.3:o:netapp:h300s_firmware:-:*:*:*:*:*:*:*
cpe:2.3:o:netapp:h500s_firmware:-:*:*:*:*:*:*:*
cpe:2.3:o:netapp:h700s_firmware:-:*:*:*:*:*:*:*
cpe:2.3:o:netapp:h300e_firmware:-:*:*:*:*:*:*:*
cpe:2.3:o:netapp:h500e_firmware:-:*:*:*:*:*:*:*
cpe:2.3:o:netapp:h700e_firmware:-:*:*:*:*:*:*:*
cpe:2.3:o:netapp:h410s_firmware:-:*:*:*:*:*:*:*
cpe:2.3:o:netapp:h410c_firmware:-:*:*:*:*:*:*:*
cpe:2.3:a:netapp:cloud_backup:-:*:*:*:*:*:*:*
cpe:2.3:a:siemens:sinec_infrastructure_network_services:*:*:*:*:*:*:*:*
cpe:2.3:a:oracle:http_server:12.2.1.3.0:*:*:*:*:*:*:*
cpe:2.3:a:oracle:http_server:12.2.1.4.0:*:*:*:*:*:*:*

More vulnerabilities in Isc Bind

CVE-2008-0122 — Critical (CVSS 10.0): Off-by-one error in the inet_network function in libbind in ISC BIND 9.4.2 and earlier, as used in libc in FreeBSD 6.2…
CVE-2001-0011 — Critical (CVSS 10.0): Buffer overflow in nslookupComplain function in BIND 4 allows remote attackers to gain root privileges.
CVE-2001-0013 — Critical (CVSS 10.0): Format string vulnerability in nslookupComplain function in BIND 4 allows remote attackers to gain root privileges.
CVE-2001-0010 — Critical (CVSS 10.0): Buffer overflow in transaction signature (TSIG) handling code in BIND 8 allows remote attackers to gain root privileges.
CVE-2000-1029 — Critical (CVSS 10.0): Buffer overflow in host command allows a remote attacker to execute arbitrary commands via a long response to an AXFR…
CVE-1999-0837 — Critical (CVSS 10.0): Denial of service in BIND by improperly closing TCP sessions via so_linger.

All CVEs affecting Isc Bind →