01 Record

CVE-2021-23017

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

UnratedPUBLISHEDCNA: f5

CNA base scoreUnratedNo CNA CVSS vector

View raw JSON

02 Description

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

03 Exploitation and scoring

Exploitation: Not assessed. CISA has not published an exploitation assessment for this record, and it is not in the KEV catalog. That is an absence of assessment, not a finding of no risk.
SSVC decision: Not assessed by CISA
EPSS probability: 53.46% probability of exploitation activity in the next 30 days.
EPSS percentile: Equal to or higher than the score of 98.8% of scored records. A rank, not a probability.
NVD base score: 7.7 (CVSS v3.x), scored by the NVD independently of the CNA.
NVD CVSS vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L
NVD analysis status: Modified. NVD last modified this record on 2026-06-17.
Red Hat severity: Important. Red Hat's rating for its own products, not a CVSS rating.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

04 Metadata

Published

2021-06-01 12:28Z5 YR AGO

Last updated

2024-08-03 18:58Z2 YR AGO

Reserved

2021-01-06

Assigning CNA

Record state

PUBLISHED

Severity

Not rated by the issuing CNA

CNA CVSS vector

Not published by the issuing CNA

Weaknesses

CWE-193Off-by-one ErrorBase

Data version

5.1

Document digest

6e40ef8893cfd058b26f4f6a075af6bbb4bb7e135a576a39fcb30a14add5c366

05 Affected products

VendorProductVersionsPlatforms

n/aNginx Web Server, Nginx PlusNginx Web Server versions 0.6.18 thru 1.20.0 before 1.20.1, Nginx plus versions R13 thru R23 before R23 P1. Nginx plus version R24 before R24 P1—

06 References

support.f5.comhttps://support.f5.com/csp/article/K12331123%2Cx_refsource_MISC
mailman.nginx.orghttp://mailman.nginx.org/pipermail/nginx-announce/2021/000300.htmlx_refsource_MISC
lists.apache.org[apisix-notifications] 20210607 [GitHub] [apisix-website] Serendipity96 opened a new pull request #362: feat: add new bloghttps://lists.apache.org/thread.html/r6fc5c57b38e93e36213e9a18c8a4e5dbd5ced1c7e57f08a1735975ba%40%3Cnotifications.apisix.apache.org%3Emailing-listx_refsource_MLIST
lists.apache.org[apisix-notifications] 20210608 [GitHub] [apisix-website] liuxiran commented on a change in pull request #362: docs: added "Apache APISIX not affected by NGINX CVE-2021-23017"https://lists.apache.org/thread.html/r37e6b2165f7c910d8e15fd54f4697857619ad2625f56583802004009%40%3Cnotifications.apisix.apache.org%3Emailing-listx_refsource_MLIST
lists.apache.org[apisix-notifications] 20210608 [GitHub] [apisix-website] netlify[bot] edited a comment on pull request #362: docs: added "Apache APISIX not affected by NGINX CVE-2021-23017"https://lists.apache.org/thread.html/rf318aeeb4d7a3a312734780b47de83cefb7e6995da0b2cae5c28675c%40%3Cnotifications.apisix.apache.org%3Emailing-listx_refsource_MLIST
lists.apache.org[apisix-notifications] 20210608 [GitHub] [apisix-website] liuxiran merged pull request #362: docs: added "Apache APISIX not affected by NGINX CVE-2021-23017"https://lists.apache.org/thread.html/r4d4966221ca399ce948ef34884652265729d7d9ef8179c78d7f17e7f%40%3Cnotifications.apisix.apache.org%3Emailing-listx_refsource_MLIST
lists.apache.org[apisix-notifications] 20210608 [apisix-website] branch master updated: docs: added "Apache APISIX not affected by NGINX CVE-2021-23017" (#362)https://lists.apache.org/thread.html/rf232eecd47fdc44520192810560303073cefd684b321f85e311bad31%40%3Cnotifications.apisix.apache.org%3Emailing-listx_refsource_MLIST
lists.fedoraproject.orgFEDORA-2021-b37cffac0dhttps://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/GNKOP2JR5L7KCIZTJRZDCUPJTUONMC5I/vendor-advisoryx_refsource_FEDORA
lists.fedoraproject.orgFEDORA-2021-393d698493https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/7SFVYHC7OXTEO4SMBWXDVK6E5IMEYMEE/vendor-advisoryx_refsource_FEDORA
www.oracle.comhttps://www.oracle.com/security-alerts/cpuoct2021.htmlx_refsource_MISC
security.netapp.comhttps://security.netapp.com/advisory/ntap-20210708-0006/x_refsource_CONFIRM
www.oracle.comhttps://www.oracle.com/security-alerts/cpujan2022.htmlx_refsource_MISC
www.oracle.comhttps://www.oracle.com/security-alerts/cpuapr2022.htmlx_refsource_MISC
packetstormsecurity.comhttp://packetstormsecurity.com/files/167720/Nginx-1.20.0-Denial-Of-Service.htmlx_refsource_MISC

07 Fixed in

AlmaLinux 8

nginx
Fixed

A version is affected if any line below covers it.
- Affected before 1:1.16.1-2.module_el8.4.0+2470+68135136.1.alma
- Affected before 1:1.16.1-2.module_el8.5.0+35+6a1225c3.1.alma
- Affected before 1:1.18.0-3.module_el8.4.0+2472+f736ed63.1.alma
- Affected before 1:1.18.0-3.module_el8.5.0+36+48437aab.1.alma
- Affected before 1:1.20.1-1.module_el8.5.0+2611+ab304644.alma
- Affected before 1:1.20.1-1.module_el8.6.0+2782+a022aca3.alma
nginx-all-modules
Fixed

A version is affected if any line below covers it.
- Affected before 1:1.16.1-2.module_el8.4.0+2470+68135136.1.alma
- Affected before 1:1.18.0-3.module_el8.4.0+2472+f736ed63.1.alma
- Affected before 1:1.20.1-1.module_el8.5.0+2611+ab304644.alma
- Affected before 1:1.20.1-1.module_el8.6.0+2782+a022aca3.alma
nginx-filesystem
Fixed

A version is affected if any line below covers it.
- Affected before 1:1.16.1-2.module_el8.4.0+2470+68135136.1.alma
- Affected before 1:1.18.0-3.module_el8.4.0+2472+f736ed63.1.alma
- Affected before 1:1.20.1-1.module_el8.5.0+2611+ab304644.alma
- Affected before 1:1.20.1-1.module_el8.6.0+2782+a022aca3.alma
nginx-mod-http-image-filter
Fixed

A version is affected if any line below covers it.
- Affected before 1:1.16.1-2.module_el8.4.0+2470+68135136.1.alma
- Affected before 1:1.16.1-2.module_el8.5.0+35+6a1225c3.1.alma
- Affected before 1:1.18.0-3.module_el8.4.0+2472+f736ed63.1.alma
- Affected before 1:1.18.0-3.module_el8.5.0+36+48437aab.1.alma
- Affected before 1:1.20.1-1.module_el8.5.0+2611+ab304644.alma
- Affected before 1:1.20.1-1.module_el8.6.0+2782+a022aca3.alma
nginx-mod-http-perl
Fixed

A version is affected if any line below covers it.
- Affected before 1:1.16.1-2.module_el8.4.0+2470+68135136.1.alma
- Affected before 1:1.16.1-2.module_el8.5.0+35+6a1225c3.1.alma
- Affected before 1:1.18.0-3.module_el8.4.0+2472+f736ed63.1.alma
- Affected before 1:1.18.0-3.module_el8.5.0+36+48437aab.1.alma
- Affected before 1:1.20.1-1.module_el8.5.0+2611+ab304644.alma
- Affected before 1:1.20.1-1.module_el8.6.0+2782+a022aca3.alma
nginx-mod-http-xslt-filter
Fixed

A version is affected if any line below covers it.
- Affected before 1:1.16.1-2.module_el8.4.0+2470+68135136.1.alma
- Affected before 1:1.16.1-2.module_el8.5.0+35+6a1225c3.1.alma
- Affected before 1:1.18.0-3.module_el8.4.0+2472+f736ed63.1.alma
- Affected before 1:1.18.0-3.module_el8.5.0+36+48437aab.1.alma
- Affected before 1:1.20.1-1.module_el8.5.0+2611+ab304644.alma
- Affected before 1:1.20.1-1.module_el8.6.0+2782+a022aca3.alma
nginx-mod-mail
Fixed

A version is affected if any line below covers it.
- Affected before 1:1.16.1-2.module_el8.4.0+2470+68135136.1.alma
- Affected before 1:1.16.1-2.module_el8.5.0+35+6a1225c3.1.alma
- Affected before 1:1.18.0-3.module_el8.4.0+2472+f736ed63.1.alma
- Affected before 1:1.18.0-3.module_el8.5.0+36+48437aab.1.alma
- Affected before 1:1.20.1-1.module_el8.5.0+2611+ab304644.alma
- Affected before 1:1.20.1-1.module_el8.6.0+2782+a022aca3.alma
nginx-mod-stream
Fixed

A version is affected if any line below covers it.
- Affected before 1:1.16.1-2.module_el8.4.0+2470+68135136.1.alma
- Affected before 1:1.16.1-2.module_el8.5.0+35+6a1225c3.1.alma
- Affected before 1:1.18.0-3.module_el8.4.0+2472+f736ed63.1.alma
- Affected before 1:1.18.0-3.module_el8.5.0+36+48437aab.1.alma
- Affected before 1:1.20.1-1.module_el8.5.0+2611+ab304644.alma
- Affected before 1:1.20.1-1.module_el8.6.0+2782+a022aca3.alma

Arch Linux

nginx
Fixed in 1.20.1-1
nginx-mainline
Fixed in 1.21.0-1

Source: Arch Linux Security Tracker, the Arch Linux security team. Reformatted by exploit.cc.

CloudLinux 8

nginx
Fixed

A version is affected if any line below covers it.
- Affected before 1:1.16.1-2.module_el8.4.0+2470+68135136.1.alma
- Affected before 1:1.16.1-2.module_el8.5.0+35+6a1225c3.1.alma
- Affected before 1:1.18.0-3.module_el8.4.0+2472+f736ed63.1.alma
- Affected before 1:1.18.0-3.module_el8.5.0+36+48437aab.1.alma
- Affected before 1:1.20.1-1.module_el8.5.0+2611+ab304644.alma
- Affected before 1:1.20.1-1.module_el8.6.0+2782+a022aca3.alma
nginx-all-modules
Fixed

A version is affected if any line below covers it.
- Affected before 1:1.16.1-2.module_el8.4.0+2470+68135136.1.alma
- Affected before 1:1.18.0-3.module_el8.4.0+2472+f736ed63.1.alma
- Affected before 1:1.20.1-1.module_el8.5.0+2611+ab304644.alma
- Affected before 1:1.20.1-1.module_el8.6.0+2782+a022aca3.alma
nginx-filesystem
Fixed

A version is affected if any line below covers it.
- Affected before 1:1.16.1-2.module_el8.4.0+2470+68135136.1.alma
- Affected before 1:1.18.0-3.module_el8.4.0+2472+f736ed63.1.alma
- Affected before 1:1.20.1-1.module_el8.5.0+2611+ab304644.alma
- Affected before 1:1.20.1-1.module_el8.6.0+2782+a022aca3.alma
nginx-mod-http-image-filter
Fixed

A version is affected if any line below covers it.
- Affected before 1:1.16.1-2.module_el8.4.0+2470+68135136.1.alma
- Affected before 1:1.16.1-2.module_el8.5.0+35+6a1225c3.1.alma
- Affected before 1:1.18.0-3.module_el8.4.0+2472+f736ed63.1.alma
- Affected before 1:1.18.0-3.module_el8.5.0+36+48437aab.1.alma
- Affected before 1:1.20.1-1.module_el8.5.0+2611+ab304644.alma
- Affected before 1:1.20.1-1.module_el8.6.0+2782+a022aca3.alma
nginx-mod-http-perl
Fixed

A version is affected if any line below covers it.
- Affected before 1:1.16.1-2.module_el8.4.0+2470+68135136.1.alma
- Affected before 1:1.16.1-2.module_el8.5.0+35+6a1225c3.1.alma
- Affected before 1:1.18.0-3.module_el8.4.0+2472+f736ed63.1.alma
- Affected before 1:1.18.0-3.module_el8.5.0+36+48437aab.1.alma
- Affected before 1:1.20.1-1.module_el8.5.0+2611+ab304644.alma
- Affected before 1:1.20.1-1.module_el8.6.0+2782+a022aca3.alma
nginx-mod-http-xslt-filter
Fixed

A version is affected if any line below covers it.
- Affected before 1:1.16.1-2.module_el8.4.0+2470+68135136.1.alma
- Affected before 1:1.16.1-2.module_el8.5.0+35+6a1225c3.1.alma
- Affected before 1:1.18.0-3.module_el8.4.0+2472+f736ed63.1.alma
- Affected before 1:1.18.0-3.module_el8.5.0+36+48437aab.1.alma
- Affected before 1:1.20.1-1.module_el8.5.0+2611+ab304644.alma
- Affected before 1:1.20.1-1.module_el8.6.0+2782+a022aca3.alma
nginx-mod-mail
Fixed

A version is affected if any line below covers it.
- Affected before 1:1.16.1-2.module_el8.4.0+2470+68135136.1.alma
- Affected before 1:1.16.1-2.module_el8.5.0+35+6a1225c3.1.alma
- Affected before 1:1.18.0-3.module_el8.4.0+2472+f736ed63.1.alma
- Affected before 1:1.18.0-3.module_el8.5.0+36+48437aab.1.alma
- Affected before 1:1.20.1-1.module_el8.5.0+2611+ab304644.alma
- Affected before 1:1.20.1-1.module_el8.6.0+2782+a022aca3.alma
nginx-mod-stream
Fixed

A version is affected if any line below covers it.
- Affected before 1:1.16.1-2.module_el8.4.0+2470+68135136.1.alma
- Affected before 1:1.16.1-2.module_el8.5.0+35+6a1225c3.1.alma
- Affected before 1:1.18.0-3.module_el8.4.0+2472+f736ed63.1.alma
- Affected before 1:1.18.0-3.module_el8.5.0+36+48437aab.1.alma
- Affected before 1:1.20.1-1.module_el8.5.0+2611+ab304644.alma
- Affected before 1:1.20.1-1.module_el8.6.0+2782+a022aca3.alma

Derived from AlmaLinux 8. Partial coverage: only packages taken from AlmaLinux 8 are listed.

Debian 12

nginx
Fixed in 1.18.0-6.1

Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.

Debian 13

nginx
Fixed in 1.18.0-6.1

Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.

Debian 14

nginx
Fixed in 1.18.0-6.1

Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu 18.04 LTS

nginx
Fixed in 1.14.0-0ubuntu1.9

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu 20.04 LTS

nginx
Fixed in 1.18.0-0ubuntu1.2

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu Pro 14.04 LTS

nginx
Fixed in 1.4.6-1ubuntu3.9+esm2
Available with Ubuntu Pro (Infra-only): https://ubuntu.com/pro

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu Pro 16.04 LTS

nginx
Fixed in 1.10.3-0ubuntu0.16.04.5+esm1
Available with Ubuntu Pro (Infra-only): https://ubuntu.com/pro

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

A release or ecosystem missing from this list has no record here. It may be unaffected or not covered by the source. Source notices and licences.