CVE-2021-23017

65

FAUCET Score

CVE-2021-23017 is a high-severity vulnerability in the nginx resolver that allows a remote attacker to cause a 1-byte memory overwrite, potentially leading to a worker process crash or other impacts. This vulnerability affects products from f5, fedoraproject, netapp, openresty, and oracle. With a CVSS score of 7.7 (High), it has a network attack vector and high attack complexity, indicating a significant risk. While not on the KEV catalog, an exploit for Denial of Service is available on ExploitDB, and it has garnered notable community discussion and media coverage, suggesting active interest.

Impacted Technologies

Vendor	Product	Version(s)	CPE
		>= 0.6.18, < 1.20.1CPE matchmatch criteria	cpe:2.3:a:f5:nginx::::::::
		< 1.19.3.2CPE matchmatch criteria	cpe:2.3:a:openresty:openresty::::::::
		33CPE matchmatch criteria	cpe:2.3:o:fedoraproject:fedora:33:::::::*
		34CPE matchmatch criteria	cpe:2.3:o:fedoraproject:fedora:34:::::::*
		Range not provided by sourceCPE matchmatch criteria	cpe:2.3:a:netapp:ontap_select_deploy_administration_utility:-:::::::*

CVSS Data

CVSS version used by this source: 3.1

7.7HIGH

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

Attack Vector

NETWORK

Attack Complexity

HIGH

Privileges Required

NONE

User Interaction

NONE

Scope

UNCHANGED

Confidentiality Impact

HIGH

Integrity Impact

HIGH

Availability Impact

LOW

Exploitability Score

2.2

Impact Score

5.5

CvssVersion

3.1

Exploit Intelligence

EPSS Score

53.46%

Probability of exploitation in next 30 days

EPSS Percentile

98.9%

Percentile rank of EPSS score among Peer Group

As of 2026-07-27

Model: v2026.06.15

ExploitDB: EDB-50973 · Jul 11, 2022

This CVE's current EPSS score of 0.5346 is in the 98th percentile among its peer group of 8,918 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.2 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 (40)

dahuapatch availablevia llm_extracted

Fixed in: 1.20.1+

dfinitypatch availablevia llm_extracted

Fixed in: 1.21.0

jfrogpatch availablevia llm_extracted

Fixed in: 1.21.0

liferaypatch availablevia llm_extracted

Fixed in: 1.20.1

microsoftpatch availablevia msrc

Product: cm1 nginx 1.20.1-1 on CBL Mariner 1.0Fixed in: 1.20.1-1

microsoftpatch availablevia msrc

Product: 17079-16820Fixed in: 1.20.1-1

netgearpatch availablevia llm_extracted

Fixed in: 1.21.0+, 1.20.1+

opensshpatch availablevia llm_extracted

Fixed in: 1.21.0

oraclepatch availablevia nvd_reference

power_bipatch availablevia llm_extracted

Fixed in: 1.20.1

redhatpatch availablevia redhat_api

Product: 3scale API Management 2.11 on RHEL 8Fixed in: 3scale-amp2/toolbox-rhel8:1.6.0-7

redhatpatch availablevia redhat_api

Product: 3scale API Management 2.11 on RHEL 8Fixed in: 3scale-amp2/zync-rhel8:1.14.0-3

redhatpatch availablevia redhat_api

Product: Red Hat Advanced Cluster Management for Kubernetes 2.1 for RHEL 8Fixed in: rhacm2/acm-must-gather-rhel8:v2.1.11-2

redhatpatch availablevia redhat_api

Product: Red Hat Advanced Cluster Management for Kubernetes 2.3 for RHEL 7Fixed in: rhacm2/management-ingress-rhel7:v2.3.3-3

redhatpatch availablevia redhat_api

Product: Red Hat Ansible Tower 3.8 for RHEL 7Fixed in: ansible-tower-38/ansible-tower-rhel7:3.8.4-1

redhatpatch availablevia redhat_api

Product: Red Hat Automation Hub 4.2 for RHEL 7Fixed in: automation-hub-0:4.2.5-1.el7pc

redhatpatch availablevia redhat_api

Product: Red Hat Automation Hub 4.2 for RHEL 7Fixed in: python-galaxy-ng-0:4.2.5-2.el7pc

redhatpatch availablevia redhat_api

Product: Red Hat Automation Hub 4.2 for RHEL 7Fixed in: python-pulpcore-0:3.7.6-1.el7pc

redhatpatch availablevia redhat_api

Product: Red Hat Automation Hub 4.2 for RHEL 8Fixed in: automation-hub-0:4.2.5-1.el8pc

redhatpatch availablevia redhat_api

Product: Red Hat Automation Hub 4.2 for RHEL 8Fixed in: python-galaxy-ng-0:4.2.5-2.el8pc

redhatpatch availablevia redhat_api

Product: Red Hat Automation Hub 4.2 for RHEL 8Fixed in: python-pulpcore-0:3.7.6-1.el8pc

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8Fixed in: nginx:1.18-8040020210526100943.522a0ee4

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8Fixed in: nginx:1.16-8040020210526102347.522a0ee4

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8Fixed in: nginx:1.20-8050020211221125012.c5368500

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8.1 Extended Update SupportFixed in: nginx:1.16-8010020210526102741.c27ad7f8

redhatpatch availablevia redhat_api

Product: Red Hat Enterprise Linux 8.2 Extended Update SupportFixed in: nginx:1.16-8020020210526102648.4cda2c84

redhatpatch availablevia redhat_api

Product: Red Hat Software Collections for Red Hat Enterprise Linux 7Fixed in: rh-nginx118-nginx-1:1.18.0-3.el7

redhatpatch availablevia redhat_api

Product: Red Hat Software Collections for Red Hat Enterprise Linux 7Fixed in: rh-nginx116-nginx-1:1.16.1-6.el7

redhatpatch availablevia redhat_api

Product: Red Hat Software Collections for Red Hat Enterprise Linux 7.7 EUSFixed in: rh-nginx118-nginx-1:1.18.0-3.el7

redhatpatch availablevia redhat_api

Product: Red Hat Software Collections for Red Hat Enterprise Linux 7.7 EUSFixed in: rh-nginx116-nginx-1:1.16.1-6.el7

redhatpatch availablevia redhat_api

Product: 3scale API Management 2.11 on RHEL 8Fixed in: 3scale-amp2/apicast-gateway-rhel8:1.20.0-6

redhatpatch availablevia redhat_api

Product: 3scale API Management 2.11 on RHEL 7Fixed in: 3scale-amp2/system-rhel7:1.15.0-8

redhatpatch availablevia redhat_api

Product: 3scale API Management 2.11 on RHEL 7Fixed in: 3scale-amp2/memcached-rhel7:1.4.16-38

redhatpatch availablevia redhat_api

Product: 3scale API Management 2.11 on RHEL 7Fixed in: 3scale-amp2/3scale-rhel7-operator:1.14.0-4

redhatpatch availablevia redhat_api

Product: 3scale API Management 2.11 on RHEL 7Fixed in: 3scale-amp2/3scale-rhel7-operator-metadata:2.11.0-16

redhatpatch availablevia redhat_api

Product: 3scale API Management 2.11 on RHEL 8Fixed in: 3scale-amp2/backend-rhel8:1.14.0-3

redhatpatch availablevia redhat_api

Product: 3scale API Management 2.11 on RHEL 7Fixed in: 3scale-amp2/apicast-rhel7-operator-metadata:2.11.0-9

redhatpatch availablevia redhat_api

Product: 3scale API Management 2.11 on RHEL 7Fixed in: 3scale-amp2/apicast-rhel7-operator:1.14.0-3

terraformpatch availablevia llm_extracted

Fixed in: 1.21.0

redhatend of lifevia redhat_api

Product: Red Hat Enterprise Linux 8Fixed in: nginx:1.14/nginx

Vendor Advisories (10)

microsoft2021-Jun/CVE-2021-23017Important

A security issue in nginx resolver was identified which might allow an attacker who is able to forge UDP packets from the DNS server to cause 1-byte memory overwrite resulting in worker process crash or potential other impact.

redhatCVE-2021-23017Important

nginx: Off-by-one in ngx_resolver_copy() when labels are followed by a pointer to a root domain name

dfinityllm-dfinity-7df11d2d0d88a2f5MEDIUM

1-byte memory overwrite in resolver

power_billm-power_bi-3b0b7437da3aa0deMEDIUM

1-byte memory overwrite in resolver

opensshllm-openssh-10dbf95c1473333eMEDIUM

1-byte memory overwrite in resolver

liferayllm-liferay-05361178f391f994MEDIUM

1-byte memory overwrite in resolver

jfrogllm-jfrog-84ea3ac3fdce1df8MEDIUM

1-byte memory overwrite in resolver

dahuallm-dahua-5ce839bbec1f0dc7MEDIUM

1-byte memory overwrite in resolver

terraformllm-terraform-a1778cbd6e919dc9MEDIUM

1-byte memory overwrite in resolver

netgearllm-netgear-5385c33c9edaaba0MEDIUM

1-byte memory overwrite in resolver

References

mailman.nginx.org / pipermail/nginx-announce/2021/000300.html

Mailing ListPatchVendor Advisory

packetstormsecurity.com / files/167720/Nginx-1.20.0-Denial-Of-Service.html

Third Party AdvisoryVDB Entry

lists.apache.org / thread.html/r37e6b2165f7c910d8e15fd54f4697857619ad2625f56583802004009%40%3Cnotifications.apisix.apache.org%3E

lists.apache.org / thread.html/r4d4966221ca399ce948ef34884652265729d7d9ef8179c78d7f17e7f%40%3Cnotifications.apisix.apache.org%3E

lists.apache.org / thread.html/r6fc5c57b38e93e36213e9a18c8a4e5dbd5ced1c7e57f08a1735975ba%40%3Cnotifications.apisix.apache.org%3E

lists.apache.org / thread.html/rf232eecd47fdc44520192810560303073cefd684b321f85e311bad31%40%3Cnotifications.apisix.apache.org%3E

lists.apache.org / thread.html/rf318aeeb4d7a3a312734780b47de83cefb7e6995da0b2cae5c28675c%40%3Cnotifications.apisix.apache.org%3E

lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/7SFVYHC7OXTEO4SMBWXDVK6E5IMEYMEE

lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/GNKOP2JR5L7KCIZTJRZDCUPJTUONMC5I

security.netapp.com / advisory/ntap-20210708-0006

Third Party Advisory

support.f5.com / csp/article/K12331123%2C

oracle.com / security-alerts/cpuapr2022.html

PatchThird Party Advisory

oracle.com / security-alerts/cpujan2022.html

PatchThird Party Advisory

oracle.com / security-alerts/cpuoct2021.html

PatchThird Party Advisory