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Fencer Vulns
high 7.7

CVE-2021-23017 in the critical feed json

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 ca…

published 2021-06-01 5 y ago modified 2026-09-08 2 mo ago also BIT-nginx-2021-23017 , BIT-nginx-gateway-2021-23017 , EUVD-2021-10135

cvss
7.7
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
53.5%
EPSS 53.5% chance of exploitation in 30 days, percentile 98%
public exploits
1
Exploit-DB

Summary

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.

Patch / fix

  • bitnami nginx 1.20.1
  • bitnami nginx-gateway 1.20.1
  • f5 nginx 1.20.1
  • openresty openresty 1.19.3.2
  • oracle blockchain_platform 21.1.2
  • oracle goldengate 21.4.0.0.0
  • nginx Debian 14, Debian 13, Debian 12 1.18.0-6.1

debian advisories DEBIAN-CVE-2021-23017

  • nginx Ubuntu 18.04 LTS 1.14.0-0ubuntu1.9
  • nginx Ubuntu 20.04 LTS 1.18.0-0ubuntu1.2
  • nginx Ubuntu Pro 14.04 LTS 1.4.6-1ubuntu3.9+esm2
  • nginx Ubuntu Pro 16.04 LTS 1.10.3-0ubuntu0.16.04.5+esm1

ubuntu advisories UBUNTU-CVE-2021-23017

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • nginx RHEL 8 1:1.20.1-1.module+el8.5.0+13723+ab304644
  • nginx-mod-mail RHEL 8 1:1.20.1-1.module+el8.5.0+13723+ab304644
  • nginx-filesystem RHEL 8 1:1.20.1-1.module+el8.5.0+13723+ab304644
  • nginx-mod-stream RHEL 8 1:1.20.1-1.module+el8.5.0+13723+ab304644
  • nginx-all-modules RHEL 8 1:1.20.1-1.module+el8.5.0+13723+ab304644
  • nginx-mod-http-perl RHEL 8 1:1.20.1-1.module+el8.5.0+13723+ab304644
  • nginx-mod-http-xslt-filter RHEL 8 1:1.20.1-1.module+el8.5.0+13723+ab304644
  • nginx-mod-http-image-filter RHEL 8 1:1.20.1-1.module+el8.5.0+13723+ab304644

red hat advisories RHSA-2022:0323RHSA-2021:2290RHSA-2021:2278RHSA-2021:2259RHSA-2021:2258RHBA-2021:2955

  • nginx SLES for SAP 15 SP1, SLES 15 SP1-LTSS, SLES 15 SP1-BCL +6 more 1.16.1-6.13.1
  • nginx SLE Module for Server Applications 15 SP3 1.19.8-3.3.1
  • nginx SLE Module for Server Applications 15 SP2 1.16.1-3.3.1
  • nginx SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 1.16.1-3.15.1

suse advisories SUSE-SU-2021:1839-1SUSE-SU-2021:1815-1SUSE-SU-2021:1814-1SUSE-SU-2021:1792-1

  • nginx openSUSE Tumbleweed 1.21.3-1.4
  • nginx openSUSE Leap 15.3 1.19.8-3.3.1
  • nginx openSUSE Leap 15.2 1.16.1-lp152.2.3.1

opensuse advisories openSUSE-SU-2024:11092-1openSUSE-SU-2021:1815-1openSUSE-SU-2021:0835-1

  • nginx AlmaLinux 8 1:1.20.1-1.module_el8.6.0+2782+a022aca3.alma
  • nginx AlmaLinux 8 1:1.20.1-1.module_el8.5.0+2611+ab304644.alma
  • nginx-mod-mail AlmaLinux 8 1:1.20.1-1.module_el8.6.0+2782+a022aca3.alma
  • nginx-mod-mail AlmaLinux 8 1:1.20.1-1.module_el8.5.0+2611+ab304644.alma
  • nginx-filesystem AlmaLinux 8 1:1.20.1-1.module_el8.5.0+2611+ab304644.alma
  • nginx-filesystem AlmaLinux 8 1:1.20.1-1.module_el8.6.0+2782+a022aca3.alma
  • nginx-mod-stream AlmaLinux 8 1:1.20.1-1.module_el8.6.0+2782+a022aca3.alma
  • nginx-mod-stream AlmaLinux 8 1:1.20.1-1.module_el8.5.0+2611+ab304644.alma

almalinux advisories ALSA-2022:0323ALSA-2021:2290ALSA-2021:2259

  • nginx Rocky Linux 8 1:1.20.1-1.module+el8.6.0+791+48a2bb9d
  • nginx Rocky Linux 8 1:1.20.1-1.module+el8.5.0+729+3f70613e
  • nginx Rocky Linux 8 1:1.16.1-2.module+el8.4.0+543+efbf198b.1
  • nginx Rocky Linux 8 1:1.18.0-3.module+el8.4.0+544+e40554cf.1

rocky linux advisories RLSA-2022:0323RLSA-2021:2290RLSA-2021:2259

  • nginx Alpine 3.10 1.16.1-r3
  • nginx Alpine 3.11 1.16.1-r7
  • nginx Alpine 3.12 1.18.0-r2
  • nginx Alpine 3.13 1.18.0-r14
  • nginx Alpine 3.24, Alpine 3.23, Alpine 3.22 +8 more 1.20.1-r0

alpine advisories ALPINE-CVE-2021-23017

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • nginx-mainline Arch Linux 1.21.0-1
  • nginx Arch Linux 1.20.1-1

arch linux advisories AVG-1987AVG-1988

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-23017 updated cvss 8.1

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

  • Red Hat Enterprise Linux 8 nginx, nginx-mod-mail, nginx-filesystem, nginx-mod-stream, nginx-all-modules, nginx-mod-http-perl, +2 more
    affected: no fix planned “Will not fix”
  • Red Hat 3Scale AMP 2.11 3scale-amp2/system-rhel7 1.15.0-8, 3scale-amp2/zync-rhel8 3scale2.11.0, 3scale-amp2/backend-rhel8 3scale2.11.0, 3scale-amp2/toolbox-rhel8 3scale2.11.0, 3scale-amp2/memcached-rhel7 3scale2.11.0, 3scale-amp2/3scale-rhel7-operator 3scale2.11.0, +4 more
    fixed: vendor fix RHSA-2021:3851
  • Red Hat Advanced Cluster Management for Kubernetes 2.1 for RHEL 8 rhacm2/acm-must-gather-rhel8 v2.1.11-2
    fixed: vendor fix RHSA-2021:3653
  • Red Hat Ansible Tower 3.8 for RHEL 7 ansible-tower-38/ansible-tower-rhel7 3.8.4-1
    fixed: vendor fix RHBA-2021:3472
  • Red Hat Automation Hub 4.2 for RHEL 7 automation-hub 4.2.5-1.el7pc, python-pulpcore 3.7.6-1.el7pc, python-galaxy-ng 4.2.5-2.el7pc, python3-pulpcore 3.7.6-1.el7pc, python3-galaxy-ng 4.2.5-2.el7pc Red Hat Automation Hub 4.2 for RHEL 8 automation-hub 4.2.5-1.el8pc, python-pulpcore 3.7.6-1.el8pc, python-galaxy-ng 4.2.5-2.el8pc, python3-pulpcore 3.7.6-1.el8pc, python3-galaxy-ng 4.2.5-2.el8pc
    fixed: vendor fix RHBA-2021:2955
  • Red Hat Enterprise Linux AppStream (v. 8) nginx 1.20.1-1.module+el8.5.0+13723+ab304644, nginx 1.16.1-2.module+el8.4.0+11155+68135136.1, nginx 1.18.0-3.module+el8.4.0+11152+f736ed63.1, nginx-mod-mail 1.20.1-1.module+el8.5.0+13723+ab304644, nginx-filesystem 1.20.1-1.module+el8.5.0+13723+ab304644, nginx-mod-mail 1.16.1-2.module+el8.4.0+11155+68135136.1, +18 more Red Hat Enterprise Linux AppStream EUS (v. 8.1) nginx 1.16.1-1.module+el8.1.0+11153+6c3a40a9.1, nginx-mod-mail 1.16.1-1.module+el8.1.0+11153+6c3a40a9.1, nginx-filesystem 1.16.1-1.module+el8.1.0+11153+6c3a40a9.1, nginx-mod-stream 1.16.1-1.module+el8.1.0+11153+6c3a40a9.1, nginx-all-modules 1.16.1-1.module+el8.1.0+11153+6c3a40a9.1, nginx-mod-http-perl 1.16.1-1.module+el8.1.0+11153+6c3a40a9.1, +2 more Red Hat Enterprise Linux AppStream EUS (v. 8.2) nginx 1.16.1-1.module+el8.2.0+11154+636e4c3b.1, nginx-mod-mail 1.16.1-1.module+el8.2.0+11154+636e4c3b.1, nginx-filesystem 1.16.1-1.module+el8.2.0+11154+636e4c3b.1, nginx-mod-stream 1.16.1-1.module+el8.2.0+11154+636e4c3b.1, nginx-all-modules 1.16.1-1.module+el8.2.0+11154+636e4c3b.1, nginx-mod-http-perl 1.16.1-1.module+el8.2.0+11154+636e4c3b.1, +2 more
    fixed: vendor fix RHSA-2021:2290
  • Red Hat Software Collections for Red Hat Enterprise Linux Server (v. 7) rh-nginx116-nginx 1.16.1-6.el7, rh-nginx118-nginx 1.18.0-3.el7, rh-nginx116-nginx-mod-mail 1.16.1-6.el7, rh-nginx118-nginx-mod-mail 1.18.0-3.el7, rh-nginx116-nginx-mod-stream 1.16.1-6.el7, rh-nginx118-nginx-mod-stream 1.18.0-3.el7, +6 more Red Hat Software Collections for Red Hat Enterprise Linux Server EUS (v. 7.7) rh-nginx116-nginx 1.16.1-6.el7, rh-nginx118-nginx 1.18.0-3.el7, rh-nginx116-nginx-mod-mail 1.16.1-6.el7, rh-nginx118-nginx-mod-mail 1.18.0-3.el7, rh-nginx116-nginx-mod-stream 1.16.1-6.el7, rh-nginx118-nginx-mod-stream 1.18.0-3.el7, +6 more Red Hat Software Collections for Red Hat Enterprise Linux Workstation (v. 7) rh-nginx116-nginx 1.16.1-6.el7, rh-nginx118-nginx 1.18.0-3.el7, rh-nginx116-nginx-mod-mail 1.16.1-6.el7, rh-nginx118-nginx-mod-mail 1.18.0-3.el7, rh-nginx116-nginx-mod-stream 1.16.1-6.el7, rh-nginx118-nginx-mod-stream 1.18.0-3.el7, +6 more
    fixed: vendor fix RHSA-2021:2278
  • Red Hat Enterprise Linux 9 nginx, nginx-core, nginx-mod-mail, nginx-filesystem, nginx-mod-stream, nginx-all-modules, +3 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Timeline

  1. Published
  2. First public exploit (EDB-50973)

Exploit prediction

53.46% chance of exploitation in the next 30 days, higher than 98% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • EDB-50973 Nginx 1.20.0 - Denial of Service (DOS) remote, 2022-07-11

CVSS scores

assigned by version score vector
NVD 3.1 7.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L
NVD 2.0 6.8 AV:N/AC:M/Au:N/C:P/I:P/A:P
OSV 3.1 7.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L

Affected packages

ecosystem package affected fixed in
bitnami nginx
>=0.6.18, <1.20.1
1.20.1
bitnami nginx-gateway
>=0.6.18, <1.20.1
1.20.1

Affected products

  • n/a Nginx Web Server, Nginx Plus

Classification

Weakness
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.