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Fencer Intel
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 5y ago modified 2mo 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

Is CVE-2021-23017 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

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, 2026-11-09).

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 Intel 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.