CVE-2021-23017

Exp

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.

Published: 2021-06-01 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-23017 is rated High Exploit Risk (80.8/100): CVSS High severity, with high exploitation likelihood (EPSS 73.54%, 99th percentile). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2021-23017

EDB-ID Source Kind Published Link
50973 exploit_db edb 2022-07-11 Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2021-23017

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-05-22 73.17% 73.54% +0.38%
2 2026-05-04 73.54% 73.17% -0.38%
3 2026-04-21 — 73.54% —

Full EPSS history (89 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-23017

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.7 3.1 HIGH
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:L)
Might cause slowdowns, glitches, or partial disruption—not a full brick.
 2.2 5.5 [email protected]
6.8 2.0 MEDIUM
AV:N/AC:M/Au:N/C:P/I:P/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:P)
Partial availability impact.
 8.6 6.4 [email protected]

Weakness enumeration for CVE-2021-23017

OS Trackers for CVE-2021-23017

vendor priority summary link
alpine critical CVE-2021-23017: 1 source package rows (nginx); 32 state rows across 10 repos (3.10-main, 3.11-main, 3.12-main, 3.17-main, 3.18-main, 3.19-main, 3.20-main, 3.21-main, 3.22-main, edge-main); fixed 12, open 20. https://security.alpinelinux.org/vuln/CVE-2021-23017
debian not yet assigned CVE-2021-23017 not yet assigned priority: Debian including 1 source packages (nginx), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2021-23017
gentoo high CVE-2021-23017: 1 GLSA(s) (202105-38), 1 atom(s) (www-servers/nginx); latest impact high. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2021-23017
redhat high — https://access.redhat.com/security/cve/CVE-2021-23017
suse high CVE-2021-23017 severity important: SUSE including 29 source package names (1.19-3.1:nginx-1.19.8-3.3.1, nginx-1.16.1-3.15.1, …), 56 product×package rows across 28 product lines (Container suse/rmt-nginx, SUSE CaaS Platform 4.0, … (28 product lines)): Fixed 56. https://www.suse.com/security/cve/CVE-2021-23017/
ubuntu medium CVE-2021-23017 medium priority: Ubuntu including 1 source packages (nginx), 9 status rows across 9 suites (bionic, focal, groovy, hirsute, impish, jammy, trusty, upstream, xenial): released 8, needs-triage 1. https://ubuntu.com/security/CVE-2021-23017

Affected software / configurations for CVE-2021-23017

Vendor Product Version Raw CPE
f5 nginx >= 0.6.18, < 1.20.1 cpe:2.3:a:f5:nginx:*:*:*:*:*:*:*:*
openresty openresty < 1.19.3.2 cpe:2.3:a:openresty:openresty:*:*:*:*:*:*:*:*
fedoraproject fedora 33 cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*
fedoraproject fedora 34 cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*
netapp ontap_select_deploy_administration_utility — cpe:2.3:a:netapp:ontap_select_deploy_administration_utility:-:*:*:*:*:*:*:*
oracle blockchain_platform < 21.1.2 cpe:2.3:a:oracle:blockchain_platform:*:*:*:*:*:*:*:*
oracle communications_control_plane_monitor 3.4 cpe:2.3:a:oracle:communications_control_plane_monitor:3.4:*:*:*:*:*:*:*
oracle communications_control_plane_monitor 4.2 cpe:2.3:a:oracle:communications_control_plane_monitor:4.2:*:*:*:*:*:*:*
oracle communications_control_plane_monitor 4.3 cpe:2.3:a:oracle:communications_control_plane_monitor:4.3:*:*:*:*:*:*:*
oracle communications_control_plane_monitor 4.4 cpe:2.3:a:oracle:communications_control_plane_monitor:4.4:*:*:*:*:*:*:*
oracle communications_fraud_monitor >= 3.4, <= 4.4 cpe:2.3:a:oracle:communications_fraud_monitor:*:*:*:*:*:*:*:*
oracle communications_operations_monitor 3.4 cpe:2.3:a:oracle:communications_operations_monitor:3.4:*:*:*:*:*:*:*
oracle communications_operations_monitor 4.2 cpe:2.3:a:oracle:communications_operations_monitor:4.2:*:*:*:*:*:*:*
oracle communications_operations_monitor 4.3 cpe:2.3:a:oracle:communications_operations_monitor:4.3:*:*:*:*:*:*:*
oracle communications_operations_monitor 4.4 cpe:2.3:a:oracle:communications_operations_monitor:4.4:*:*:*:*:*:*:*
oracle communications_session_border_controller 8.4 cpe:2.3:a:oracle:communications_session_border_controller:8.4:*:*:*:*:*:*:*
oracle communications_session_border_controller 9.0 cpe:2.3:a:oracle:communications_session_border_controller:9.0:*:*:*:*:*:*:*
oracle enterprise_communications_broker 3.3.0 cpe:2.3:a:oracle:enterprise_communications_broker:3.3.0:*:*:*:*:*:*:*
oracle enterprise_session_border_controller 8.4 cpe:2.3:a:oracle:enterprise_session_border_controller:8.4:*:*:*:*:*:*:*
oracle enterprise_session_border_controller 9.0 cpe:2.3:a:oracle:enterprise_session_border_controller:9.0:*:*:*:*:*:*:*
oracle enterprise_telephony_fraud_monitor 3.4 cpe:2.3:a:oracle:enterprise_telephony_fraud_monitor:3.4:*:*:*:*:*:*:*
oracle enterprise_telephony_fraud_monitor 4.2 cpe:2.3:a:oracle:enterprise_telephony_fraud_monitor:4.2:*:*:*:*:*:*:*
oracle enterprise_telephony_fraud_monitor 4.3 cpe:2.3:a:oracle:enterprise_telephony_fraud_monitor:4.3:*:*:*:*:*:*:*
oracle enterprise_telephony_fraud_monitor 4.4 cpe:2.3:a:oracle:enterprise_telephony_fraud_monitor:4.4:*:*:*:*:*:*:*
oracle goldengate < 21.4.0.0.0 cpe:2.3:a:oracle:goldengate:*:*:*:*:*:*:*:*

References for CVE-2021-23017

URL Tags
http://mailman.nginx.org/pipermail/nginx-announce/2021/000300.html Mailing List Patch Vendor Advisory
http://packetstormsecurity.com/files/167720/Nginx-1.20.0-Denial-Of-Service.html Third Party Advisory VDB Entry
https://lists.apache.org/thread.html/r37e6b2165f7c910d8e15fd54f4697857619ad2625f56583802004009%40%3Cnotifications.apisix.apache.org%3E
https://lists.apache.org/thread.html/r4d4966221ca399ce948ef34884652265729d7d9ef8179c78d7f17e7f%40%3Cnotifications.apisix.apache.org%3E
https://lists.apache.org/thread.html/r6fc5c57b38e93e36213e9a18c8a4e5dbd5ced1c7e57f08a1735975ba%40%3Cnotifications.apisix.apache.org%3E
https://lists.apache.org/thread.html/rf232eecd47fdc44520192810560303073cefd684b321f85e311bad31%40%3Cnotifications.apisix.apache.org%3E
https://lists.apache.org/thread.html/rf318aeeb4d7a3a312734780b47de83cefb7e6995da0b2cae5c28675c%40%3Cnotifications.apisix.apache.org%3E
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/7SFVYHC7OXTEO4SMBWXDVK6E5IMEYMEE/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/GNKOP2JR5L7KCIZTJRZDCUPJTUONMC5I/
https://security.netapp.com/advisory/ntap-20210708-0006/ Third Party Advisory
https://support.f5.com/csp/article/K12331123%2C
https://www.oracle.com/security-alerts/cpuapr2022.html Patch Third Party Advisory
https://www.oracle.com/security-alerts/cpujan2022.html Patch Third Party Advisory
https://www.oracle.com/security-alerts/cpuoct2021.html Patch Third Party Advisory
cvelogic Threat Intelligence